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JQX 

W.  J.  BEAL,  M.S.,  Ph.D. 

PROFESSOR  OF   BOTANY   AND   FORESTRY    IN   MICHIGAN 
AGRICULTURAL  COLLEGE 


GINN  &  COMPANY 

BOSTON  ■  NEW  YORK  •  CHICAGO  •  LONDON 


Copyright,  189S 
By  WILLIAM  J.  BEAL 


ALL  RIGHTS   RESERVED 
311.1 


tR^t   atlicnsum   33resg 

GINN   &   COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


PEEFAOE 


This  little  book  is  prepared  with  the  thought  of  helping 
young  botanists  and  teachers.  Unless  the  reader  has  followed 
in  detail,  by  actual  experience,  some  of  the  modes  of  jjlant 
dispersion,  he  can  have  little  idea  of  the  fascination  it  affords, 
or  the  rich  rewards  in  store  for  patient  mvestigation. 

A  brief  list  of  contributions  to  the  subject  is  given  ;  but, 
with  very  few  exceptions,  the  statements  here  made,  imless 
otherwise  mentioned  m  the  text,  are  the  results  of  observations 
by  the  author. 

I  am  under  obligations  for  suggestions  l)y  my  colleague,  Prof. 
W.  B.  Barrows  ;  my  assistant,  Prof.  C.  F.  Wheeler  ;  and  a 
former  instructor  of  botany,  L.  H.  Dewey,  now  of  the  United 
States  Department  of  Agricultui-e.  B.  O.  Longyear,  instructor 
ui  botany,  \\dth  very  few  exceptions,  has  made  the  drawmgs. 

•  W.  J.  Beal. 

Agricultural  College,  Michigan. 


'•?OPERTV 


i/%o         "•■S5Kfi^, 


00]SrTE]N"TS. 


Chapter  1 How  Animals  Gkt  About, 

PAGE 

1.  Most  of  the  larger  animals  move  about  freely 'l 

2.  Some  animals  catch  rides  in  one  way  or  another       ....  2 


Chapter  IT.  —  Pl.^nts  Spread  by  Means  of  Roots. 

3.  Fairy  rings 4 

4.  How  nature  plants  lilies 7 

5.  Roots  hold  plants  erect  like  ropes  to  a  mast 8 

6.  How  oaks  creep  about  and  multiply 8 


Chapter  III.  —  Plants  Multiply  by  Means  of  Stems. 

7.  Two  grasses  in  fierce  contention 12 

8.  Runners  establish  new  colonies 1.3 

9.  Branches  lean  over  and  root  in  the  soil 14 

10.    Living  branches  snap  off  and  are  carried  by  water  or  wind       .         .  15 


Chapter  IV.  —  Water  Transportation  of  Plants. 

11.  Some  gi-een  buds  and  leaves  float  on  water    ......  18 

12.  Fleshy  buds  drop  off  and  sprout  in  the  mud 20 

13.  Seeds  and  fruits  as  boats  and  rafts 22 

14.  Bits  of  cork  around  the  seeds  prevent  them  from  sinking          .         .  24 

15.  An  air-tight  sack  buoys  up  seeds 25 

16.  Fruit  of  basswood  as  a  sailboat,  and  a  few  others  as  adapted  to  the  water  27 


VI 


CONTENTS. 


Chapter  V.  —  Seeds  Transported  by  Wind. 


17.  How  pigweeds  get  about 

18.  Tumbleweeds 

19.  Thin,  dry  pods,  twisted  and  bent,  drift  on  the  snow 

20.  Seeds  found  in  melting  snowdrifts      .... 

21.  Nuts  of  the  basswood  carried  on  the  snow     . 

22.  Buttonwood  balls 

23.  Seeds  that  tempt  the  wind  by  spreading  their  sails 

24.  Why  are  some  seeds  so  small  ? 

25.  Seeds  with  parachutes 

26.  A  study  of  the  dandelion 

27.  How  the  lily  sows  its  seeds 

28.  Large  pods  with  small  seeds  to  escape  from  small  holes 

29.  Seeds  kept  dry  by  an  umbrella  growing  over  them 
SO.  Shot  off  by  wind  or  animal 

31.  Seed-like  fruits  moved  about  by  twisting  awns 

32.  Grains  that  bore  into  sheep  or  dogs  or  the  sand 

33.  Winged  fruits  and  seeds  fall  with  a  whirl 

34.  Plants  which  preserve  a  portion  of  their  seeds  for  an  emergency 


PAGE 
.       30 

31 
.     35 

36 
.     37 

39 
.     40 

42 
.     43 

44 
.     46 

47 
.     48 

50 
.     51 

51 
.     52 

54 


Chapter  VI.  —  Plants  that  Shoot  Off  their  Spores  or  Seeds. 


35.  Dry  pods  twist  as  they  split  open  and  throw  the  seeds 

36.  A  seed  case  that  tears  itself  from  its  moorings  . 


57 
59 


Chapter  VIT.  —  Plants  that  are  Carried  by  Animals. 

37.  Squirrels  leave  nuts  in  queer  places  and  plant  some  of  them         .         .  61 

38.  Birds  scatter  nuts 63 

39.  Do  birds  digest  all  they  eat  ? 64 

40.  Color,  odor,  and  pleasant  taste  of  fruits  are  advertisements      .         .  65 

41.  The  meddlesome  crow  lends  a  hand 68 

42.  Ants  distribute  some  kinds  of  seeds 69 

43.  Cattle  carry  away  living  plants  and  seeds 70 

44.  Water-fowl  and  muskrats  carry  seeds  in  mud 71 


CONTENTS.  vii 

PAGE 

45.  Wliy  some  seeds  are  sticky 72 

46.  Three  devices  of  Virginia  knotweed 7.3 

47.  Hooks  rendered  harmless  till  time  of  need 74 

48.  Diversity  of  devices  in  the  rose  family  for  seed  sowing      ...  76 

49.  Grouse,  fox,  and  dog  carry  burs    ........  7(! 

50.  Seeds  enough  and  to  spare 78 


Chapter  VIII.  —  Man  Disperses  Seeds  and  Plants. 

51.  Burs  stick  to  clothing 80 

52.  Man  takes  plants  westward,  though  a  few  migrate  eastward      .         .        83 


Ch.\pter  IX.  —  Some  Reasons  for  Plant  Migration. 

53.  Plants  are  not  charitable  beings 84 

54.  Plants  migrate  to  improve  their  condition 85 

55.  Fruit  grown  in  a  new  country  is  often  fair 85 

56.  Much  remains  to  be  discovered 80 

Bibliography      ............  89 


SEED    DISPERSAL. 


j;»4c 


CHAPTER    I. 
HOW   ANIMALS    GET    ABOUT. 

1.  Most  of  the  larger  animals  move  about  freely.  — 
When  danger  threatens,  the  rabbit  bounds  away  in  long 
jumps,  seeking  protection  in  a  hollow  tree,  a  log,  or  a 
hole  in  the  ground.  When  food  becomes  scarce,  squir- 
rels quickly  shift  to  new  regions.  Coons,  bears,  skunks, 
and  porcupines  move  from  one  neighborhood  to  another. 
When  the  thickets  disappear  and  hunters  abound,  wild 
turkeys  and  partridges  retreat  on  foot  or  by  wing.  When 
the"leaves  fall  and  the  cold  winds  blow,  wild  geese  leave 
the  lakes  in  secluded  northern  homes,  and  with  their 
families,  reared  during  the  summer,  go  south  to  spend 
the  winter.  Turtles  swim  from  pond  to  pond  or  crawl 
from  the  water  to  the  sand  bank,  where  they  lay  and  cover 
their  eggs.  Fishes  swim  up  or  down  the  creek  with 
changing  seasons,  or  seek  deep  or  shallow  water  as  their 
needs  require.  Beetles  and  butterflies,  when  young,  crawl 
about  for  food  and  shelter,  and  when  older  use  their 
wings  in  going  long  distances. 

These  examples  only  serve  to  recall  to  mind  what 
every  boy  or  girl  knows  and  has  known  ever  since  he 


2  SEED  DISPERSAL. 

can  remember  —  that  most  animals  move  about  when- 
ever they  want  to,  or  whenever  other  anhnals  will  let 
them. 

2.  Some  animals  catch  rides  in  one  way  or  another.  — 
Some  small  animals,  like  lice,  ticks,  and  tiny  spiders, 
walk  slowly  and  only  for  short  distances.  If,  because  of 
scarcity  of  food,  they  are  suddenly  seized  with  the  desire 
to  move  for  a  long  distance,  what  are  they  to  do  ?  On 
such  occasions  ticks  and  lice  watch  quietly  the  first 
opportunity,  catch  on  to  the  feet  of  birds  or  flying  insects 
or  other  animals  which  may  happen  to  come  their  way, 
and,  like  a  boy  catching  on  to  a  farmer's  sleigh,  ride  till 
they  get  far  enough,  then  jump  off  or  let  go,  to  explore  the 
surrounding  country  and  see  whether  it  is  fit  to  live  in. 
If  for  some  reason  a  spider  grows  dissatisfied  and  wants 
to  leave  the  home  spot,  she  climbs  to  the  top  of  some 
object  and  spins  out  a  fine,  long  web  ;  this  floats  in  the 
air,  and  after  a  while  becomes  so  long  and  light  that  the 
wind  will  bear  the  thread  and  the  spmner  for  a  consider- 
able distance,  no  one  knows  how  far.  These  facts  about 
lice  and  spiders  show  how  wingless  insects  can  go  long 
distances  without  wings  of  their  own. 

How  is  it  with  plants?  The  woods,  fields,  marshes, 
roadsides  ever  abound  with  interesting  objects  provided 
with  strange  devices  waiting  to  be  studied  by  inquisitive 
girls  and  boys  in  and  out  of  school,  and  this  finding  out 
of  nature's  puzzles  is  one  of  the  deepest  pleasures  of  life. 

How  quickly  a  mould   attacks  and  creeps  or  spreads 


BOW  ANIMALS  GET  ABOUT.  3 

tliroLigli  a  basin  of  berries  every  one  knows.  The  mould 
is  as  much  a  plant  as  the  bush  that  produced  the  berries ; 
it  comes  from  a  small  spore,  which  takes  the  place  of  a 
bud  or  sprout  or  seed.  The  decay  of  a  tree  begins  where 
a  limb  or  root  has  been  injured,  and  whether  the  timber 
is  living  or  dead,  this  decay  results  from  the  growth  of 
some  one  or  more  low  forms  of  plant  life  w^hich  enter  the 
timber  in  certain  places  and  slowly  or  quickly  penetrate 
and  affect  other  portions  more  or  less  remote. 


CHAPTER    II. 
PLANTS    SPREAD   BY   MEANS   OF    ROOTS. 

3.  Fairy  rings.  —  Several  low  forms  of  plant  life,  such 
as  Marasniius  oreades,  Sjyathularia  Jiavida,  and  some  of  the 
puifballs,  start  in  isolated  spots  in  the  grass  of  a  lawn  or 
pasture,  and  spread  each  year  from  a  few  inches  to  a  foot 
or  more  in  every  direction,  usually  in  the  form  of  a  circle  ; 
at  the  end  of  fifteen  years  some  of  these  circles  acquire 
a  diameter  of  fifteen  to  twenty  feet  or  more.  These  are 
known  as  fairy  rings.  Before  science  dispelled  the  illusion 
they  were  believed  to  have  been  the  work  of  witches, 
elves,  or  evil  spirits,  from  which  arose  the  name. 

Several  kinds  of  lichens  and  mosses  and  the  like,  grow- 
ing on  the  barks  of  trees,  fence  boards,  and  low  ground, 
spread  slowly  in  the  manner  of  fairy  rings. 

However,  the  spreading  is  not  always  a  slow,  creeping 
process,  for  sometimes  these  low  plants  spread  over  an 
incredible  distance  in  a  short  space  of  time.  In  some 
instances  they  appear  suddenly  almost  an3rw"here,  and  at 
any  season  of  the  year.  They  are  all  minute  and  exist 
in  countless  numbers,  and  their  devices  for  securing  wide 
dispersion  are  so  various  as  to  entitle  them  to  first  rank 
in  this  respect.  Some  send  off  spores  with  a  sharp  puff, 
as  if  shot  from  a  little  gun.     Some  of  these  spores  float 


PLANTS  SPREAD  BY  MEANS  OF  ROOTS.  5 

on  water,  and  some  are  sticky  and  thus  gain  free  rides. 
It  is  not  at  all  improbable  that  some  are  carried  by  the 
winds  across  oceans  and  continents. 

It  is  well  known  that  many  of  the  lower  species  of 
plants  are  more  widely  distributed  over  the  earth  than 
most  of  the  higher  plants.  Every  cloud  from  a  ripe  puft"- 
ball  consists  of  thousands  of  spores  started  on  the  wings 
of  the  wind  for  an  unknown  journey.  Their  habits  are 
not  past  finding  out,  but  to  examine  them  a  person  needs 
a  good  microscope.  Most  of  them  have  no  special  com- 
mon name,  and  with  one  or  two  exceptions  further  men- 
tion of  the  mode  of  distribution  of  this  fascinating  portion 
of  plant  life  cannot  here  be  made. 

In  our  botanic  garden  was  planted  a  patch  six  feet 
across  of  what  is  known  as  Oswego  tea,  bee  balm,  or  red- 
flowered  bergamot,  an  interesting  plant  with  consider- 
able beauty.  It  grew  well  for  a  year,  the  next  year  it 
failed  to  some  extent,  and  on  the  third  most  of  the  plants 
died,  or  nearly  died,  excepting  the  spreading  portion  all 
around  the  margin.  This  is  a  fairy  ring  of  another  type, 
and  represents  a  very  slow  mode  of  travel.  As  further 
illustrations  of  this  topic  study  common  yarrow,  betony, 
several  mints,  common  iris,  loosestrife,  coreopsis,  gill-over- 
the-ground,  several  wild  sunflowers,  horehound,  and  many 
other  perennials  that  have  grown  for  a  long  time  without 
transplanting. 

The  roots  of  plants  are  seldom  much  observed,  because 
they  are  out  of  sight.     In  soft  ground  the  roots  of  the 


SEED  DISPERSAL. 


common  or  black  locust  extend  from  twenty  to  forty  feet 
in  each  direction,  and  almost  anywhere  along  these  roots 
buds  may  appear,  and  a  shoot  spring  up  and  become  a  tree. 
This  peculiarity  is  worth  as  much  to  locusts  in  the 
matter  of  spreading  as  though  the  parent  trees  were  able  to 
move  about.  A  number  of  kinds  of  poplars  and  willows, 
ailanthus,  some  of  the  elms,  ashes,  sweet 
potatoes,  milkweeds,  Canada  thistles,  and 
others  behave  in  a  similar  manner. 
Little  bits  of  Canada-thistle  root  half  an 
inch  long  may  send  forth  buds,  and  each 
bud  grow  to  be  an  independent  plant. 

Roots  have 
a  peculiarity 
not  usually 
known.  They 
stretch  out  and 
crook  about 
here  and  there, 
penetrating 
the  crevices  of 
the  soil  wher- 
ever there  is  the  least  chance,  and  the  matured  portions 
begin  to  shorten,  reminding  one  somewhat  of  an  angle- 
worm when  one  end  has  been  stepped  on.  By  this 
shortening  process  the  top  or  crown  of  a  dandelion  or 
plantam  is  pulled  down  beneath  the  surface  of  the 
ground. 


Fig.  1. 


Buds  and  shoots  sprouting  from  roots  of  the 
common  locust. 


PLANTS  SPREAD  BY  MEANS  OF  ROOTS.  7 

4.  How  nature  plants  lilies.  —  Lilies  grow  from  bulbs 
which  are  planted  six  inches  beneath  the  surface.  Do 
you  know  liow  nature  plants  them  ?  A  seed  starts  and 
becomes  a  small  plant  on  the  surface  of  the  leaf  mould  or 
a  little  beneath  ;  little  roots  push  downward  and  to  right 
and  left ;  and  later,  after  getting  a  good  hold  below  with 
numerous  branchlets,  the  slender  roots  shorten  and  tug 
away  at  the  tiny  bulb  above,  as  much  as  to  say,  ^'  Come 
down  a  little  into  mother  earth,  for  cold  winter  is  approach- 
ing and  there  will  be  danger  from  frost."  The  young 
bulb  is  drawn  down  an  inch  more  or  less,  the  slender 
roots  perish  with  the  growing  year,  but  the  bulb  is  pre- 
served. The  seedling  was  well  planned;  for  while  it  had 
yet  tender  leaves  during  its  first  year,  starch  and  proto- 
plasm were  stored  up  in  the  thickened  scales  of  the  bulb. 
During  the  second  spring  some  of  this  food  in  store  is 
used  to  send  down  another  set  of  slender  roots  with  the 
message  to  gather  in  more  water,  potash,  phosphorus, 
nitrogen,  and  other  substances  to  help  grow  a  larger  bulb. 
In  late  summer  and  autumn  the  new  roots  contract  and 
pull  away  at  the  greater  bulb,  and  down  it  goes  into  the 
ground  another  inch  or  so.  I  have  a  theory  as  to  how  it 
finally  comes  to  be  drawn  down  just  deep  enough  and  no 
more,  but  I  will  not  venture  to  give  it.  This  process  is 
repeated  from  year  to  year  till  the  proper  dej)th  is  reached 
for  preserving  the  full-grown  bull).  And  this  is  the  way 
nature  plants  bulbs. 

In  a  similar  manner  young  slender  roots  well  anchored 


8  SEED   DISPERSAL. 

in  the  soil,  at  or  near  the  close  of  the  growing  season,  pull 
downward  and  outward  large  numbers  of  bulblets  that 
form  around  a  parent  bulb  of  some  kinds  of  leeks,  tulips, 
star-of-bethlehem,  globe  hyacinth,  and  monkshood.  The 
pull  of  the  roots  is  much  greater  to  one  side  than  down- 
ward, because  most  of  the  longest  roots  extend  sidewise. 
Marilaun  reports  that  a  cfertain  lawn  in  Vienna  was  mown 
so  frequently  that  tulips  could  not  go  to  seed,  but  after 
twenty  years,  from  a  very  few  bulbs  planted  near  each 
other,  a  space  twenty  paces  in  diameter  was  well  covered 
by  tulips.  And  this  is  one  way  tulips  travel,  slow  and 
sure. 

5.  Roots  hold  plants  erect  like  ropes  to  a  mast.  —  Did 
you  ever  lift  vines  of  cucumbers,  squashes,  and  the  like, 
where  they  had  rooted  at  the  joints,  and  observe  how 
forlorn  they  looked  after  the  operation,  with  leaves  tipped 
over,  unable  to  remain  erect  ?  While  growing,  the  stem 
zigzags  or  wmds  about  more  or  less,  and  thus  enables  it 
to  hold  the  leaves  erect;  besides,  the  tendrils  catch  on  to 
weeds  and  curl  up  tight,  and  the  roots  at  tlie  joints  are 
drawn  taut  on  each  side  after  the  manner  mentioned 
above,  and  act  like  ropes  to  a  mast  to  hold  the  stem  in  its 
place,  and  thus  help  to  hold  the  leaf  above  erect. 

6.  How  oaks  creep  about  and  multiply.  —  Oaks  come 
from  acorns ;  everybody  knows  that.  The  nuts  are  pro- 
duced in  abundance,  and  those  of  the  white  oak  send  out 
pretty  good  tap  roots  on  the  same  year  they  fall.  Some 
of  the  nuts  roll  down  the  knoll  or  are  carried  about  by 


PLANTS  SPREAD  BY  MEANS  OF  ROOTS. 


squirrels  or  birds,  as  mentioned  elsewhere 
you  one  thing  that  I  discovered 
the  white  oaks  were  doing  in 
the  sand  of  the  Jack-pine 
plains  of  Michigan.  In  dry 
weather  the  dead  grass,  sticks, 
and  logs  are  often  burned, 
which  kills  much  or  all  that 
is  growing  above  ground.  In 
this  way  little  maples,  ashes, 
w^itch-hazels,  willows,  huckle- 
berries,  blackberries,   sweet 


Let  me  tell 


Fig.  3.  —  Grub,  or  remains  of  a  white  oak,  doubt- 
less at  one  time  much  like  Fig.  2,  but  now 
decayed  in  the  middle,  including  its  main 
root ;  sprouting  on  the  margins,  fartlii-r  and 
fartluT  out  after  the  tops  were  killeil,  to  the 
ground 


Fig.  2.  —  Small  tree,  "  grub,"  of 
white  oak  many  times  killed 
back  ;  finally  dead  at  the 
middle  and  sprouting  on  the 
majgins. 

ferns,  service  berries, 
aspens,  oaks,  and  others 
are  often  killed  back, 
but  afterward  sprout 
up  again  and  again, 
and,  after  repeated 
burnings,  form  each  a 
large  rough  mass  popu- 
larly known  as  a  gimh. 
The  grubs  of  the  oak 
are  well   known ;    the 


10 


SEED  DISPERSAL. 


large  ones  weighing  from  75  to  100  pounds  each.  To  plow 
land  where  grubs  abound  requires  a  stout  plow  and  sev- 
eral pairs  of  horses  or  oxen. 

A  small  white  oak,  after  it  has  been  many  times  killed 
to  the  ground,  dies  in  the  middle  and  sprouts  at  the 
margins,  and  finally  the  main  root  perishes,  and  two  roots, 
with  branches  a  little  distance  apart,  support  each  a  clus- 
ter of  stems  above  ground. 


Fig.  4.  —  Grub,  or  remains  of  a  Avhite  oak,  still  older  than  the  one 
represented  in  Fig.  3.  A  hole  appears  where  the  tap  root  has 
rotted  away.  The  right-hand  portion  is  already  dividing,  and  in 
time,  if  often  killed  back,  we  might  find  several  distinct  oaks  as 
descendants  from  orie  acorn. 


There  can  be  no  doubt  that  young  oak  trees  slowly 
move  in  this  manner  from  one  jD^ace  to  another.  If  in 
fifty  years  we  have  two  distinct  grubs  or  branches,  three 
or  four  feet  apart,  where  the  connecting  part  has  finally 
died  out,  I  see  no  reason  why  in  another  fifty  years  each 
one  of  the  two  may  not  again  have  spread  and  divided, 


PLANTS  SPREAD  BY  MEANS  OF  ROOTS. 


11 


giving  us  at  least  four  grubs,  or  clusters  of  sprouts,  all 
originally  coming  from  one  acorn  ;  and  so  the  matter 
might  go  on.  This  is  slow  traveling,  I  admit,  but  there  is 
nothing  to  hinder  nature  from  taking  all  the  time  she 
wants. 


Fig.  6.  — Part  of  a  grub  of  white  oak,  still  alive  and  spreading  over 
the  ground,  the  central  portions  dying,  the  margins  alive  and 
spreading. 


CHAPTER   III. 


PLANTS  MULTIPLY   BY   MEANS   OF    STEMS. 

7.  Two  grasses  in  fierce  contention.  —  In  growing  a 
lawn  at  the  Michigan  Agricultural  College,  a  little  Ber- 
muda grass    was  s^     yd       ^^    scattered    with     June 


grass 

most  interesting, 
for  six  weeks  in 
usually  abounds 
June  grass  thrives 
the  dry,  hot  weeks 


struggle    has     been 

In     the     spring     and 

autumn,     when     moisture 

and   the  weather  is   cool, 

and  little  else  is   seen.      In 

of  July   and   August,    June 


Fig.  6.  — Kootstock  of  quick  grass  which  has  grown  through  a  potato,  and  in  this  way  may 
be  carried  to  another  held  or  another  farm. 

grass  rests  and  the  Bermuda,  which  continues  to  spread, 
assumes  control  of  the  lawn,  with  but  little  of  the  June 
grass  in  sight.     Each  struggles  for  possession  and  does 


PLANTS  MULTIPLY  BY  MEANS  OF  STEMS.         13 

the  best  it  can,  and  to  some  extent  one  supplements  the 
other,  with  the  result  that  at  all  times  from  spring  to  fall 
there  is  a  close  mat  of  living  green  which  delights  the  eye 
and  is  pleasant  to  the  feet  that  tread  upon  it.  In  soft 
ground,  with  plenty  of  room,  a  bit  of  quick  or  quack 
grass,  or  Bermuda,  will  extend  in  a  year  three  to  five  feet 
or  more  in  one  direction. 

June  grass,  quick  grass,  Bermuda  grass,  redtop,  and 
white  clover,  wherever  opportunity  offers,  spread  by 
means  of  jointed  stems,  creeping  and  rooting  at  every 
joint  on  the  surface  of  the  ground  or  a  little  way  below. 
These  are  not  roots  at  all,  but  true  stems  somewhat  in 
disguise.  Here  may  also  be  mentioned,  as  having  similar 
habit,  artichokes,  peppermint,  spearmint,  barberry,  Indian 
hemp,  bindweed,  toadflax,  matrimony  vine,  bugle-weed, 
ostrich  fern,  eagle  fern,  sensitive  fern,  coltsfoot,  St.  John's- 
wort,  sorrel,  great  willow-herb,  and  many  more. 

8.  Runners  establish  new  colonies.  —  The  spreading  of 
strawberries  by  runners  must  be  familiar  to  every  observer. 
In  1894  a  student  reported  that  a  wild  strawberry  plant 
in  the  botanic  garden  had  produced  in  that  year  1230 
plants.  Weeds  were  all  kept  away,  the  season  was  favor- 
able, the  soil  sandy ;  but  on  one  side,  witliin  a  foot  and  a 
half,  progress  was  checked  by  the  presence  of  a  large  plant 
of  another  kind.  The  multiplication  of  this  plant  by 
seeds,  in  addition  to  that  by  runners,  would  have  covered 
a  still  greater  area  of  land.  Other  plants  with  runners 
much  like  the  strawberry  are :  several  kinds  of  crowfoot. 


14  SEED  DISPERSAL. 

barren  strawberry,  cinquefoil,  strawberry  geranium,  and 
orange  hawk  weed.  Plants  of  the  star  cucumber,  one- 
seeded  cucumber,  grapes,  morning-glories,  and  others, 
spread  more  or  less  over  bushes  or  over  the  ground,  and 
are  thus  enabled  to  scatter  seeds  in  every  direction. 


Fig.  7.  —  The  runner  of  a  strawberry  plant. 


9.  Branches  lean  over  and  root  in  the  soil. — A  black 
raspberry  grows  fast  in  the  ground  and  has  to  stay  in  one 
spot  for  life.  It  has  neither  legs,  feet,  nor  wings,  and  yet 
it  can  travel.  The  bush  takes  deep  root  and  spreads  out 
its  branches,  which  are  sometimes  ten  feet  or  more  in 
length ;  the  tips  of  these  branches  curve  over  to  the 
ground  six  feet  away,  and  finally  take  root  ;  from  these 
roots  new  colonies  are  formed,  five  to  twenty  in  a  year 
from  one  bush. 

True,  the  old  roots  do  not  get  far,  and  the  new  plants 
only  get  about  six  feet  in  one  season,  but  they  have  made 
some  progress.  This  is  rather  slow  locomotion,  you  say  ; 
but  let  us  look  a  little  farther,  remembering  that  a  seed 


PLANTS  MULTIPLY  BY  MEANS  OF  STEMS. 


15 


is  a  little  plant  packed  ready  for  transportation.     This  sec- 
ond mode  of  spreading  will  be  described  on  a  future  page. 


Fig.  8.  — Plant  of  a  black  raspberry  showing  one  branch  (stolon)  with  several  tips  rooting. 


10.  Living  branches  snap  off  and  are  carried  by  water  or 
wind.  —  Some  trees  and  shrubs  among  the  willows  are 
called  snap-willows,  because  their  branches  are  very  brit- 
tle ;  on  the  least  strain  from  wdnd,  rain,  sleet,  or  snow,  the 
smaller  branches  snap  off  near  the  larger  branches  or  the 
main  trunk,  and  fall  to  the  ground.  At  first  thought 
this  brittleness  of  the  wood  might  seem  to  be  a  serious 
defect  in  the  structure  of  the  tree  or  shrub,  although 
they  seem  to  produce  branches  enough  for  their  own  use. 

But  the  brandies  which  are  strewn  all  around  after 
a  storm  often  take  root  in  the  low  ground  where  they 
fall ;  some  of  tliem  are  carried  down  stream  by  the 
current,  and,  lodging  on  the  shore  below,  produce  new 
trees  or  bushes 


During  the  winter  of  1895  and  1896  a 


16 


SEED  DISPERSAL. 


group  of  seven 
white  willows,  near 
a  brook  on  the 
c a m pus  of  the 
Michigan  Agri- 
cultural College, 
was  at  one  time 
loaded  with  sleet. 
There  was  consider- 
able snow  on  the 
ground,  which,  of 
course,  was  covered 
with  an  icy  crust. 
In  a  little  while  the 
sleet  melted  from 
the  fallen  branches 
strewn  about,  and 
a  moderate  breeze 
then  drifted  the 
smallest  of  the 
twigs  in  consider- 
able numbers  over 
the  icy  snow.  Some 
of  these  were  found 
thirty  rods  distant 
[G.  10. -Portion   fj,Qj^  ^i^g   parent 

or  a  branch  of  ^ 

the  Cottonwood  trCCS  UOt       doWU 

Fig.  9. —  Branch  of  snap-willow  root-         as  it  fell  from  .  .. 

ing  at  one  end.  the  tree.  StrCam  m  thC  Vaiicy 


PLANTS  MULTIPLY  BY  MEANS  OF  STEMS.         17 

of  the  brook,  but  up  the  stream.  Had  not  the  low  ground 
been  covered  with  a  dense  growth  of  grass,  some  of  these 
branches  might  have  started  new  trees  w'here  the  wind 
had  left  them.-' 

The  branches  on  slow-growing  limbs  of  cotton  wood 
and  large-toothed  aspen  are  much  enlarged  at  the  nodes, 
and  at  these  places  are  brittle,  often  separating  from  the 
tree  and  breaking  up  into  pieces.  Under  a  small  cotton- 
wood  were  picked  up  a  bushel  or  more  of  such  limbs,  all 
yet  alive.  These  trees  are  common  on  low  land,  and,  like 
snap-willows,  the  severed  twigs  may  find  a  chance  to  grow 
on  moist  soil.^ 

In  a  greenhouse  a  potted  plant  of  Selaginella  emiliana  (?) 
was  placed  on  the  bench  near  the  aisle,  where  it  was  often 
brushed  by  people  in  passing.  Small  branches,  not  being 
firmly  attached,  were  frequently  broken  from  the  main 
plant  and  fell  upon  the  moist  sand,  wdiere  they  rooted  in 
abundance. 

1  C.  D.  Lippincott  believes  that  this  is  a  provision  of  nature  to  dispose 
of  the  now  unnecessary  branchlets  without  leaving  a  knot.  Plant  World, 
Vol.  1,  p.  96. 

2  The  In-ittle  hraiiches  of  salix  were  noticed  by  the  author  in  Bull.  Torr. 
Bot.  Club,  Vol.  IX  (1883),  p.  89. 


CHAPTER   IV. 


WATER   TRANSPORTATION   OF    PLANTS. 

11.  Some  green  buds  and  leaves  float  on  water. — Loosely 
floating  on  slow  streams  of  the  northern  states,  m  water 
not  the  purest,  may  often  be  found  the  common  bladder- 
wort,   Utricidaria  indgcms,  producing  in  summer  a  few 

yellow  flowers   on  each 


stem,  rising  from  six  to 
twelve  inches  above  the 
water.  The  lax,  leafy 
branches  in  the  water 
are  from  six  inches  to  a 
foot  long.  The  leaves, 
or  thread-like  branches, 
are  about  half  an  inch 
long,  more  or  less,  and 
several  times  divided. 
Scattered  about  are 
large  numbers  of  flattened  scales,  or  bladders,  sometimes 
one-sixth  of  an  inch  long,  which  give  the  plant  one  of  its 
names.  For  a  long  time  the  bladders  were  thought  to 
serve  merely  as  life-preservers ;  it  was  supposed  that  they 
were  constructed  to  keep  the  plant  from  sinking  to  the 
bottom.     In  reality  these  bladders  help  preserve  the  plant 


Fig.  11. 


■  A  free  branch  and  two  buds  of 
bladderwort. 


WATER  TRANSPORTATION  OF  PLANTS.  19 

in  another  sense,  by  catching  and  killing  large  nnnibers  of 
minute  animals,  on  which  the  plant  lives  in  part.  The  tips 
of  the  stems  at  all  times  of  the  year  are  rather  compact, 
made  up  of  young  leaves  and  stems,  and  in  the  middle 
of  the  summer,  as  well  as  at  other  times,  many  may  be 
seen  severed  from  the  parent  plant,  floating  in  the  water, 
ready  to  accept  the  assistance  of  any  favorable  current  or 
breeze  and  start  out  for  homes  of  their  own  to  found  new 
colonies.  These  olive-green  tips,  or  buds,  vary  much  in 
size,  but  the  largest  are  the  size  of  the  end  of  one's 
little  finger.  Late  in  autumn  or  early  winter,  when  cold 
threatens,  the  tender  buds  contract  a  little,  and,  having 
thus  become  heavier  than  water,  slowly  go  to  the  bottom 
to  spend  the  winter  safely  protected  in  the  soft  mud. 
All  the  plant  perishes  except  these  buds.  With  the 
lengthening  days  of  spring  the  melting  ice  disappears, 
and  genial  sunshine  gives  notice  to  the  dormant  buds 
that  it  is  safe  to  come  out  again.  The  buds  begin  to 
expand,  become  lighter  than  water,  and  are  soon  seen 
spreading  out  at  the  surface  and  producing  branches  and 
leaves.  Ducks  and  other  water-fowl  not  infrequently 
carry  some  of  these  wet  buds  sticking  to  their  feathers 
or  legs. 

In  this  connection  the  following  plants  maybe  examined 
from  time  to  time :  Lemna,  Wolffia,  Anadiaris  (EJodea), 
Myriojohyllum,  Cahomba,  and  several  species  of  Potamo- 
geton.  I  have  seen  the  leaves  of  lake  cress,  Nasturtium 
lacustre,  often    spontaneously   separate    from   the    stem, 


20 


SEED  DISPERSAL. 


possibly  carrying  at  the  base  the  rudiments  of  a  small 
bud,  which  draws  on  the  floating  leaf  for  nourishment 
and  produces  a  small  plant  near  its  base.  These  ^^lants, 
floated  and  nourished  by  the  mother  leaf,  may  drift 
down  a  creek  or  across  a  pond  and 
establish  new  settlements.  In  a  similar 
manner  behave  leaves  of  the  following, 
and  perhaps  others :  Cardamine  prateiisis, 
horse-radish,  celandine,  some  water  lilies, 
and  other  plants  not  grown  in  wet  land. 
Gardeners  often  propagate  certain 
species  by  placing  leaves  on  wet  sand 
or  mud,  when  buds  spring  from  the 
margins  of  the  leaves  or  from 
some  other  portion. 

One  of  the  buttercups,  Itanun- 
culus  onultifidus,  and  very  likely 
others,  spread  over  the  mud  by  produc- 
ing runners,  much  after  the  manner  of 
a  strawberry  plant.     If,  as  in  case  of  a 
freshet,    the    plants    should    be    covered 
with  water,  they  show  their  enterprise  by 
taking  advantage  of  the  "tide";    some 
of  the  runners  are  quickly  severed,  and 
are  then  at  liberty  to  go  as  they  please. 
12.   Fleshy  buds  drop  off  and  sprout  in  the  mud.  —  One 
of  the  loosestrifes,  Lysmiacliia  stricta,  a  plant  growing  in 
bogs,  besides  reproducing  itself  by  rootstocks  and  seeds, 


Fig.  12.  —  Floating  leaf 
of  lake  cress,Xastnr- 
tium  lacustre,  with  a 
young  plant  growing 
from  the  base. 


WATER  TRANSPORTATION  OF  PLANTS. 


21 


bears  fleshy  buds  lialf  an  inch  long,  which  separate  from 
the  stems  and  take  root  in  the  nuid  near  the  parent  phint, 
or  often  float  to  another  spot.  The  buds  on  the  stemo  of 
Cicuta  hulhifera  develop  into  small  l)ulbs,  which  readily 
separate  from  the  plant.  They  then  float  on  the  water 
and  produce  new  plants.  The  tiger  lily  also  produces 
bulblets,  which   scatter  about  and  promptly  take   root. 


Fig.  13.  —  Branch  of  loosestrife  bearing 
tuber  bulblets. 


Fig.  14.  —  One  of  the  tubers 
enlarged. 


Every  person  of  good  understanding  must  have  heard  or 
read  about  seeds  carried  by  ocean  currents  or  transported 
by  lake,  pond,  creek,  or  by  muddy  current,  during,  and 
after,  a  shower  of  rain ;  in  most  of  these  the  wind  is  also 
a  prominent  factor.  Many  seeds  and  fruits,  in  some 
cases  parts,  and  even  the  whole,  of  plants  seem  to  be 
purposely  designed  for  this  mode  of  travel,  while  an 
innumerable  host  of  others  occasionally  make  use  of  it, 


22  SEED  DISPERSAL. 

although  it  may  seem  from  their  structure  and  place  of 
growth  that  they  were  made  especially  to  be  transported 
by  the  wind  or  by  -some  animal.  As  has  been  seen  in 
examples  previously  mentioned,  one  portion  of  a  plant  is 
transported  in  one  way,  and  another  portion  by  one  or 
two  other  methods. 

13.  Seeds  and  fruits  as  boats  and  rafts.  —  An  excellent 
place  in  which  to  begin  investigating  this  part  of  the 
subject  is  to  pay  a  visit  to  the  flats  of  a  creek  or  river 
late  in  a.utumn  or  in  the  spring,  after  the  water  has 
retired  to  its  narrow  channel,  and  examine  piece  after* 
piece  of  the  rubbish  that  has  been  lodged  here  and  there 
against  a  knoll  or  some  willows,  a  patch  of  rushes  or  dead 
grass.  We  are  studying  the  different  modes  by  which 
plants  travel.  In  the  driftwood  may  be  found  dry  fruits 
of  the  bladder  nut,  brown  and  light,  an  inch  and  a  half 
in  diameter.  See  how  tough  they  are ;  they  seem  to  be 
perfectly  tight,  and  even  if  one  happens  to  have  a  hole 
punched  in  its  side,  there  are  probably  two  cells  that  are 
still  tight,  for  there  are  three  in  all.  Within  are  a  few 
seeds,  hard  and  smooth.  Why  are  they  so  hard  ?  Will 
it  not  be  difficult  for  such  seeds  to  get  moist  enough  and 
soft  enough  to  enable  them  to  germinate?  The  hard 
coats  enable  the  seeds  to  remain  uninjured  for  a  long 
time  in  the  water,  in  case  one  or  two  cells  of  the  papery 
pods  are  broken  open;  and  after  the  tough  pod  has 
decayed  and  the  seeds  have  sunken  to  the  moist  earth 
among  the  sticks  and  dead  leaves,  they  can  have  all  the 


WATER  TRANSPORTATION  OF  PLANTS. 


23 


time  they  need  for  the  slow  decay  of  their  armor.     Sooner 

or  later  a  tiny  plant  is  likely  to  appear  and  produce  a 

beautiful    bush.     Engineers  are   boast- 
ing of  their  steel  ships  as  safe  and  not 

likely  to  sink,  because  there  are  several 

compartments  each  in  itself  water-tight. 

In  case  of  accident  to  one  or  two 

chambers,  the   one   or  two   remaining 

tight  will  still  float  the  whole  and  save 

the  passengers. 

I  wonder  if  the  engineers  have  not 

been  studying  the  fruit  of  the  bladder 

nut  ?    But  this  is  not  all.     Many  of  the 

dry  nuts  hang  on  all  winter,  or  for  a 

part   of    it,    rattling    in   the   wind,    as 

though  loath  to  leave.     Some  of  them 

are  torn  loose,  and  in  winter  there  will 

be  a  better  chance  than  at  any  other 

time  for  the  wind  to  do  the  seeds  a 
favor,  especially  when  there  is  snow 
on  the  ground,  for  then  they  will 
bound  along;  before  the  breeze  till 
something  interrupts  them. 

Here  among  the  rubbish  are  some 
shriveled  wild  grapes  also.  As  we 
shall  see  elsewhere,  their  best  scheme 

is  to  be  eaten  by  certain  birds,  which  do  not  digest  their 

bony  seeds;   but  in  case  some  of  them  are  left  there  is 


Fig.  15.  —Fruit  of  bladder 
nut  with  three  tight  cells. 


Fig.  16.— Shriveled  wild  grapes 
overlooked  by  birds,  now 
ready  to  float  on  w.ater,  and 
a  clean  seed  not  able  to 
float. 


24 


SEED  DISPERSAL. 


another  mode  of  travel,  not  by  wings  of  a  bird,  but  by 
floating  on  water. 

Clean  grape  seeds  sink  at  once,  but  covered  Ijy  the 
dry  skin  and  pulp,  they  float.  In  a  similar  manner  the 
dry  seeds  of  several  dogwoods  are  eaten  for  the  pulp  by 
birds,  but  in  case  any  are  left  they  behave  after  tlie 
manner  of  grapes. 

14.  Bits  of  cork  around  the  seeds  prevent  them  from  sink- 
ing. —  Narrow-leaved  dock  is  a  prominent  weed,  and  is 


Fig.  17.  —  Fruit  and  adherent  calyx  of  narrow-leaved  dock  ;  a  cross  section  and  a  naked, 
seed-like  fruit  (enlarged). 

especially  at  home  on  river  bottoms  and  on  low  land  that 
is  flooded  once  in  a  while. 

Did  you  ever  wonder  what  could  be  the  object  of  a 
round,  spongy  tubercle  on  the  outside  of  each  of  these 
sepals  which  hold  the  ripened  seed  closely  ?  I  did  not 
know  their  use  for  a  long  time,  but  now  think  I  have 
discovered  their  meaning.  They  are  not  exactly  life- 
preservers,  but  the  next  thing  to  it.     The  naked,  seed- 


WlOPERTV  OF 

Jt*W.C0LLEGFMPP4RY. 


WATER  TRANSPORTATION  OF  PLANTS. 


Fig.  18.  —  Fruit 
of  Asa- Gray 
sedge  witli  an 
inflated  sack 
about  it. 


like  fruit,  the  shape  of  the  fruit  of  buckwheat,  sinks  at 
once  when  free  from  everything  else,  but  with 
the  dry  calyx  still  attached,  it  floats  with  the 
stream. 

^5=^5.  An  air-tight  sack  buoys  up  seeds.  —  Here 
are  several  dry  fruits  of  sedges  —  plants  look- 
ing considerably  like  grasses.  There  are  a 
good  many  kinds,  and  most  of  them  grow  in 
wet  places.  The  seed-like  fruit  of  those  we 
examine  are  surrounded  each  by  a  sack  which 
is  considerably  too  large  for  it, 
as  one  would  be  likely  to  say, 
but  in  reality  it  serves  to  buoy 
the  denser  portion  within,  much 
after  the  plan  of  the  bladder  nut. 
In  some  instances  the  sack  is  rather  small, 
but  a  corky  growth  below  the  grain  helps  to 
buoy  it  on  water. 

Sedges  that  grow  on 
dry  land  usually  have 
the  sack  fitted  closely, 
instead  of  inflated,  and  the  whole 
mass  sinks  readily  in  water^  Npw 
we  see  the  probable  reason  why  the 
sack  is  inflated  in  some  species  of 
sedges  and  not  in  others. 

Here  are  some  small,  seed-like  fruits,  achenes,  not  likely 
to  be  recognized  by  every  one.    They  belong  to  the  arrow- 


FlG.  19.— Fruit  of 
Carex  commu- 
nis, an  upland 
sedge,  tliat 
readily  sinks 
•when  placed  in 
water;  the  sack 
fits  closely. 


FiQ.  20.  —  Seed-like  fruit  of 
arrowhea<l  with  corky  mar- 
gins to  float  on  water. 


26 


SEED  DISPERSAL. 


head,  Sagittaria,  found  in  shallow  ponds  or  slow  streams. 

They  are  flattened,  and  on  one  edge,  or  both,  and  at  the 

apex  is  a  spongy  ridge.  Very 
likely,  by  this  time,  the  reader 
has  snrmised  that  this  serves  the 
jDurpose  of  a  raft  to  float  the 
small  seed  within,  which  would 
sink  at  once  if  sepa- 
rated from  the  boat 
that    grew    on    its 

Fig.  21.  —  Seed-like  fruit  of  bur  reed  niarciuS.         In       this 
with  corky  lining  ready  to  float  on 

water,  and  a  naked  seed,  such  as  COUnCCtioU    may    bc 

sinks  promptly.  ;       t     i            i                        c 

studied  aciienes  oi 
water  plantain,  AUsvia,  bur  reed,  cat-tail  flag, 
arrow  grass,  burgrass,  numerous  pondweeds, 
several  buttercups,  the  hop,  nettles,  wood 
nettle,  false  nettle,  cinquefoil,  avens,  nine- 
bark,  buttonbush,  and  in  fact  a  large  number 
and  variety  of  plants  usually  found  on  river 
bottoms. 

One  of  the  lyme  grasses,  Elymus  Virginicus, 
is  a  stiff,  short  grass,  growing  along  streams. 
Each  spikelet  with  its  chaff  adheres  to  two 
empty  glumes,  stout,  thick,  and  spongy, 
which  make  a  safe  double  boat  for  trans- 
portation down  stream  whenever  the  water 
is  high  enough.  The  grains  of  rice-cut  grass,  grown 
in    ditches    and    sj^ring   brooks,    smk    if    separated,    but 


Fig.  22.  —  Grains  of 
lyme  grass  with 
two  corky  empty 
glumes  attached, 
which  serve  as  a 
raft. 


WAT  mi   TEANSPORTATION  OF  J'LANTS.  27 

in  tlie  cliaff,  as  tliey  fall  when  ripe,  they  are  good 
floaters. 

In  the  driftwood,  which  we  still  have  under  considera- 
tion, are  some  fruits  of  maple,  beech,  oak,  tulip  tree, 
locust,  and  basswood.  Maples  are  well  scattered  by  the 
wind,  but  these  seed-like  fruits  have  taken  to  the  water, 
and  a  few  still  retain  vitality.  An  acorn,  while  yet  alive, 
sinks  readily,  and  is  not  suited  for  water  navigation, 
unless  by  accident  it  rides  on  some  driftwood.  The  fruits 
of  the  tulip  tree,  locust,  and  basswood  behave  well  on  the 
water,  as  though  designed  for  the  purpose,  though  we 
naturally,  and  with  good  reason,  class  them  with  plants 
usually  distributed  by  wind. 

16.  Fruit  of  basswood  as  a  sailboat,  and  a  few  others  as 
adapted  to  the  water.  —  In  spring,  when  the  bracts  and 
fruits  of  the  basswood  are  dry  and  still  hanging  on  the 
tree,  if  a  quantity  of  them  are  shaken  off  into  the  water 
which  overflows  the  banks  of  a  stream,  many  of  these,  as 
they  reach  the  Avater,  will  assume  a  position  as  follows : 
The  nuts  spread  right  and  left  and  float ;  the  free  portion 
of  the  bract  extends  into  the  water,  while  the  portion 
adhering  to  the  peduncle  rises  obliquely  out  of  the  water 
and  serves  as  a  sail  to  draw  along  the  trailing  fruit. 
After  sailing  for  perhaps  fifteen  minutes,  the  whole  bract 
and  stem  go  under  water,  the  nuts  floating  the  whole  as 
they  continue  to  drift  with  the  wind. 

Noticeable  among  seeds  in  the  flood  wood  are  some  of 
the  milkweeds,  which  every  one  would  say  at  a  glance 


28 


SEED  DISPERSAL. 


Fig.  23.  —  Seed  of  milkweed 


were  especially  fitted  for  sailing  through  the  air,  aided 
by  their  numerous  long,  silky  hairs.  These  hairs  are  no 
hindrance  to  moving  by  water.  I  discovered  one  little 
thins:  in  reference  to  the  seed  which  makes  me  think  the 
Designer  intended  it  should  to  some 
extent  be  carried  by  water.  The  flat 
seed  has  a  margin,  or  hem,  which 
nuist  be  an  aid  to  the  wind  in  driving 
it  about ;  but  this  margin  is  thickened 
somewhat  by  a  spongy  material. 

With  the  margin  it  floats,  without 

with  a  corky  margin  en-     •,      .t  I'l'i"!  j.  a 

abiingittofloat;aseed  it  tlic  secd  suiks  ui  frcsh  watcr.     A 
with  such  margin  removed  fg^  cranbcrries  wcre  found  in  the  drift- 

sinks  at  once. 

wood.     These  contain  considerable  air 
in  the  middle,  near  where  the  seeds  are  placed, 
as  though  the  air  was  intended  to  support 
them  on  top  of  water. 

These  berries  are  colored  and  edible  — 
qualities  that  attract  the  birds.  And  here 
we  find  in  several  places  the  bulblets  of  a 
wild  garlic,  Allium  Canadense,  which  grows 
on  the  river  bottom.  These  bulblets  are 
produced  on  top  of  the  stem  with  the  flowers,  fig.  24.  -  cran- 
and  float  on  the  water.  The  seeds  of  the  inganiuTsira^e 
white  water  lilies,  and  yellow  ones  also,  by  ^^'^1'''''" '' 
special  arrangement  float  about  on  the  water 
with  the  current  or  the  wind.  The  coffee  tree  grows 
rather  sparingly  along  some  of  the  streams,  and  on  moist 


WATER  TRANSPORTATION  OF  PLANTS.  29 

land  as  far  north  as  Clinton  County,  Michigan.  The 
stout,  hard  pods  are  three  to  four  inches  long,  one  and 
one-quarter  to  one  and  one-half  inches  wide,  and  one-half 
inch  thick.  The  very  hard  seeds  are  surrounded  with 
sweet  pulp,  which  most  likely  made  it  an  inducement 
for  some  of  our  native  animals  to  devour  them  and 
thus  transport  the  undigested  seeds  to  remote  localities. 
The  pods  often  remain  on  the  trees  all  winter,  and  when 
dry,  will  float  on  the  water  of  overflowed*  streams  without 
any  injury  resulting  to  the  hard  seeds.  By  themselves  the 
seeds  sink  at  once. 


CHAPTER    V. 
SEEDS    TRANSPORTED   BY    WIND. 

17.  How  pigweeds  get  about.  —  In  winter  we  often  see 
dead  tops  of  lanlb's-qnarters  and  amaranths  —  the  smooth 
and  the  prickly  pigweeds  —  still  standing  where  they  grew 
in  the  summer.  These  are  favorite  feeding  grounds  for 
several  kinds  of  small  birds,  especially  when  snow  covers 
the  ground. 

Many  of  the  seeds,  while  still  enclosed  in  the  thin,  dry 
calyx,  and  these  clustered  on  short  branches,  drop  to  the 
snow  and  are  carried  off  by  the  wind.  Notwithstanding 
the  provision  made  for  spreading  the  seeds  by  the  aid  of 
birds  and  the  wind,  the  calyx  around  each  shiny  seed 
enables  it  to  float  also;  when  freed  from  the  calyx,  it 
drops  at  once  to  the  bottom.  Many  kinds  of  dry  fruits 
and  seeds  in  one  way  or  another  find  their  way  during 
winter  to  the  surface  of  the  ice-covered  rivers.  When  the 
rivers  break  up,  the  seeds  are  carried  down  stream,  and 
perhaps  left  to  grow  on  dry  land  after  the  water  has 
retired.  Most  of  the  commonest  plants,  the  seeds  of 
which  are  usually  transported  by  water,  are  insignificant 
in  appearance  and  without  common  names,  or  with  names 
that   are   not  well  understood.     This  is  one  reason   for 


SEEDS  TliANSroirrHI)   liV   ll/.VD.  31 

omitting  the  description  of  otlicrs  wliicli  are  ingeniously 
fitted  in  a  great  variety  of  ditt'erent  ways  for  traveling 
by  water. 

18.  Tumbleweeds.  —  Incidentally,  the  foregoing  pages 
contain  some  account  of  seeds  and  fruits  tliat  are  carried 
by  the  aid  of  wind,  in  connection  with  their  distribution 
by  other  methods ;  but  there  are  good  reasons  for  giving 
other  examples  of  seeds  carried  by  the  wind.  There  is  a 
very  common  weed  found  on  waste  ground  and  also  in 
fields  and  gardens,  which  on  good  soil,  with  plenty  of 
room  and  light,  grows  much  in  the  shape  of  a  globe  with 
a  diameter  of  two  to  three  feet.  It  is  called  Aniaranthus 
alhus  in  the  books,  and  is  one  of  the  most  prominent  of  our 
tumbleweeds.  It  does  not  start  in  the  spring  from  seed 
till  the  weather  becomes  pretty  warm.  The  leaves  are 
small  and  slender,  the  flowers  very  small,  with  no  display, 
and  surrounded  by  little  rigid,  sharp-pointed  bracts.  AYhen 
ripe  in  autumn,  the  dry,  incurved  branches  are  quite  stiff ; 
the  main  stem  near  the  ground  easily  snaps  off  and  leaves 
the  light  ball  at  the  mercy  of  the  winds.  Such  a  plant 
is  especially  at  home  on  prairies  or  cleared  fields,  whore 
there  are  few  large  obstructions  and  where  the  wind  has 
free  access. 

The  motheir  plant,  now  dead,  toiled  busily  during  the 
heat  of  summer  and  produced  thousands  of  little  seeds. 
The  best  portion  of  her  substance  went  to  produce  these 
seeds,  giving  each  a  portion  of  rich  food  for  a  start  in  life 
and  wrapping  each  in  a  glossy  black  coat.     Now  she  is 


32  SEED  DISPERSAL. 

ready  to  sacrifice  the  rest  of  her  body  to  be  tumbled 
about,  broken  in  pieces,  and  scattered  in  every  direction 
for  the  good  of  her  precious  progeny,  most  of  whom  will 
find  new  places,  where  they  will  stand  a  chance  the  next 
summer  to  grow  into  plants.  Sometimes  the  winds  are 
not  severe  enough  or  long  enough  continued,  and  these 
old  skeletons  are  rolled  into  ditches,  piled  so  high  in 
great  rows  or  masses  against  fences  that  some  are  rolled 
over  the  rest  and  pass  on  beyond.  Occasionally  some 
lodge  in  the  tops  of  low  trees,  and  many  are  entangled 
by  straggling  bushes.  In  a  day  or  two,  or  in  a  week,  or 
a  month,  the  shifting  wind  may  once  more  start  these 
wrecks  in  other  directions,  to  be  broken  up  and  scatter 
seeds  along  their  pathway. 

During  the  Middle  Ages  in  southern  Egypt  and  Arabia, 
and  eastward,  a  small  plant,  with  most  of  the  peculiarities 
of  our  tumbleweed  just  described,  was  often  seen,  and  was 
thought  to  be  a  great  wonder.  It  was  called  the  "  rose 
of  Jericho,"  though  it  is  not  a  rose  at  all,  but  a  first 
cousin  to  the  mustard,  and  only  a  small  affair  at  that, 
scarcely  as  large  as  a  cabbage  head.  A  number  of  other 
plants  of  this  habit  are  well  known  on  dry  plains  in 
various  parts  of  the  world ;  one  of  the  most  prominent  in 
the  northern  United  States  is  called  the  Russian  thistle, 
which  was  introduced  from  Russia  with  flaxseed.  In 
Dakota,  often  two,  three,  or  more  grow  into  a  community, 
making  when  dry  and  mature  a  stiff  ball  two  to  three 
feet  or  more  in  diameter. 


SEEDS  TRANSPORTED  BY  WIND. 


33 


One  of  our  peppergrasses,  Lepidium  intermedium,  some- 
times attains  the  size  and  shape  of  a  bushel  basket ;  when 
ripe,  it  is  blown  about,  sowing  seeds  wherever  it  goes. 


Fig.  25.  —  Mature  dry  plant  of  Kussiuu  thistle  as  a  tuinbleweetl.     (Uiieseventb  uatural  size.'; 

The  plants  of  the  evening:  primrose  sometimes  do  likewise, 
also  a  spurge.  Euj)liorlna  \_Preslii']  nutans,  a  weed  a  foot 
to  a  foot  and  a  half  high. 


34 


SEED  DISPERSAL. 


Low  hop  clover,  an  annual  with  yellow  flowers,  which 
has  been  naturalized  from  Europe,  has  developed  recently 
on  strong  clay  land  into  a  tumbleweed  six  inches  in 
diameter.  The  tops  of  old  witch  grass,  Panicum  ccqDillare, 
and  hair  grass,  Agrostis  hyemalis,  become  very  brittle  when 

ripe,  and  snap  from  the 
parent  stem  and  tumble 
about  singly  or  in  masses, 
scattering  seeds  by  the 
millions.  I  have  seen 
piles  of  these  thin  tops 
larger  than  a  load  of  hay 
where  they  had  blown 
against  a  grove  of  trees, 
and  in  some  cases  many 
were  caught  in  the  tops 
of  low  trees. 

Bug  seed  and  buifalo 
bur  are  tumbleweed s. 
In  autumn  the  careful 
observer  with  an  eye  to 
this  subject  will  be 
rewarded  by  finding 
many  other  plants  that 
behave  more  or  less  as  tumbleweeds.  Especially  is  this  the 
case  on  prairies.  These  are  annuals,  and  perish  at  the  close 
of  the  growing  season.  There  are  numerous  other  devices 
by  which  seeds  and  fruit  secure  transportation  by  the  wind. 


Fig.  26.  • 


-  The  top  of  old  witch  grass  as  a  tumble- 
weed.     (Reduced  two  thirds.) 


SEEDS  TEANSFORTED  BY  WIND. 


36 


f!>i 


^VJ 


19.  Thin,  dry  pods,  twisted  and  bent,  drift  on  the  snow 

The  coiiiuion  locust  tree, 
Robinia  Pseudacacia,  blos- 
soms and  produces  large 
numbers  of  thin,  flat  pods, 
which  remain  of  a  dull  color 
even  when  the  seeds  are  ripe. 
The  pods  of  the  locust  may 
wait  and  wait,  holding  fast 
for  a  lono;  time,  but  nothinii; 
comes  to  eat  them.  They 
become  dry  and  slowly  split 
apart,  each  half  of  the  pod 
usually  carrying  every  other 
seed.  Some  of  the  pods 
with  the  seeds  still  attached 
are  torn  off  by  the  wind  and 
fall  to  the  ground  sooner  or 
later,  accordmg  to  the  force 
of  the  wind.  Each  half-pod 
as  it  comes  off  is  slightly 
bent  and  twisted,  and  might 
be  considered  a  "want- 
advertisement  "  given  to  the 
wind :  "  Here  I  am,  thin, 
dry,  light  and  elastic,  twisted 

and  bent  already;  give  me  a  lift  to  bear  these  precious 
seeds  up  the  hill,  into  the  valley,  or  over  the  plain." 


ic<:^^ 


Fig.  27.  —  Two  views  of  a  balf-pod  of  com- 
mon locust,  dry,  twisted,  and  bent,  ready 
for  a  breeze. 


56    .  SEED  DISPERSAL. 

And  the  wind  is  sure  to  come  along,  a  slight  breeze 
to-day  tossing  the  half-pod  a  few  feet,  leaving  it  perhaps 
to  be  again  and  again  moved  farther  forward.  The 
writer  has  seen  these  half-pods  transported  by  this  means 
more  than  a  block.  But  many  of  the  pods  stick  to  the 
limbs  till  winter  comes.  Then  a  breeze  tears  off  a  few 
pods  and  they  fall  on  the  snow,  which  has  filled  up  all 
the  crevices  in  the  grass  and  between  the  dead  leaves  and 
rubbish.  Each  half-pod,  freighted  with  every  other  seed,  is 
admirably  constructed ;  like  an  ice  boat,  it  has  a  sail  always 
spread  to  the  breeze.  In  this  way  there  is  often  nothing 
to  hinder  some  of  the  seeds  from  goiiig  a  mile  or  two  in 
a  few  minutes,  now  and  then  striking  some  object  which 
jars  off  a  seed  or  two.  The  seeds  are  very  hard,  and  no 
doubt  purposely  so,  that  they  may  not  be  eaten  by  insects 
or  birds;  but  once  in  moist  soil,  the  covering  slowly 
sw^ells  and  decays,  allowing  the  young  plant  to  escape. 
Thus  the  locust  seeds  are  provided  with  neither  legs, 
wings,  fins,  nor  do  they  advertise  by  brilliant  hue  and 
sweet  pulp ;  but  they  travel  in  a  way  of  their  own,  which 
is  literally  on  the  wings  of  the  wind. 

20.  Seeds  found  in  melting  snowdrifts.  —  It  will  interest 
the  student  of  nature  to  collect  a  variety  of  seeds  and  dry 
fruits,  such  as  can  be  found  still  on  the  trees  and  other 
plants  in  winter,  and  try  some  of  them  when  there  is 
snow  on  the  ground  and  the  wind  blows,  to  see  how  they 
behave.  Again,  when  the  first  snow  banks  of  the  early 
winter  are  nearly  gone,  let  him  collect  and  melt  a  quantity 


SEEDS   TRANSPORTED   BY    WIND. 


37 


of  snow  and  search  for  seeds.  By  tliis  means  be  can  see, 
as  he  never  saw  before,  how  one  neighbor  snifers  from 
the  carelessness  of  another. 

21.  Nuts  of  the  basswood  carried  on  the  snow. — Here 
are  some  notes  concerning  the  distribution  of  tlie  spherical 
nuts   of   basswood.     The   small   clusters  of   fruit   pi-oject 


FKi.'js.-FniitaiuibnKt  of  ^     from  a  Quecr   bract  which 

b.-jsswooil  well  adaptt'il  for  ^^ 

moving  before  the  wind  on      ^      rcniams  attaclicd    bcforc   and 

after  falling  from  the  tree. 
This  bract,  when  dead,  is  bent 
near  the  middle  and  more  or  less 
twisted,  with  the  edges  curving 
toward  the  cluster  of  nuts.  From 
two  to  five  nuts  about  the  size  of 
peas  usually  remain  attached  till 
winter,  or  even  a  few  till  spring. 
This  bract  has  attracted  a  good  deal 
of  attention,  and  for  a  long  time  everybody  wondered 
what  could  Ije  its  use.  We  shall  see.  The  cluster  of 
nuts  and  the  bract  hang  down,  dangling  about  with 
the  least  breath  of  wind,  and  rattling  on  the  trees  l^e- 
cause  tlie  enlarged  base  of  the  stem  has  all  broken 
loose  excepting  two  slender,  woody  threads,  which  still 
hold    fast.     These    threads   are    of   different   degrees   of 


38  SEED  DISPERSAL. 

strength ;  some  break  loose  after  a  few  hard  gales,  while 
others  are  strong  enough  to  endure  many  gales,  and  thus 
they  break  off  a  few  at  a  time.  The  distance  to  which 
the  fruit  can  be  carried  depends  on  the  form  of  the 
bract,  the  velocity  of  the  wind,  and  the  smoothness  of 
the  surface  on  which  the  fruit  falls.  When  torn  from  the 
tree  the  twist  in  the  bract  enables  the  wind  to  keep  the 
cluster  rapidly  whirling  around,  and  by  whirling  it  is 
enabled  to  remain  longer  suspended  in  the  air  and  thus 
increase  the  chances  for  a  long  journey.  In  throwing 
some  of  these  from  a  third-story  window,  it  was  found 
that  a  bract  with  no  fruit  attached  would  reach  the 
ground  sooner  than  a  bract  that  bore  from  two  to  four 
solid  nuts.  The  empty  or  unloaded  bracts  tumble  and 
slide  through  the  air  endwise,  with  nothing  to  balance 
them  or  steady  their  descent,  while  the  fruit  on  other 
bracts  holds  them  with  one  side  to  the  air,  which  prolongs 
their  descent.  The  less  a  loaded  bract  whirls,  the  faster 
its  descent,  and  the  more  a  bract  whirls  when  the  wind 
blows,  the  farther  it  is  carried.  The  bract  that  is  weighted 
with  a  load  of  fruit  acts  as  a  kite  held  back  by  a  string, 
and  when  in  this  position  the  wind  lifts  the  whole  as  well 
as  carries  it  along.  Before  snow  had  fallen  in  1896,  by 
repeated  moves  on  a  well-mowed  lawn,  fruit  and  bracts 
were  carried  about  two  hundred  feet,  w^hile  with  snow  on 
the  ground  the  distance  was  almost  unlimited,  excepting 
where  there  were  obstructions,  such  as  bushes  and  fences. 
When  there  is  a  crust  on  the  snow  and  a  good  wind,  the 


SEEDS  TRANSPORTED  BY   WIND.  39 

conditions  are  almost  perfect.  Over  the  snow  the  wind 
drives  the  bracts,  which  drag  along  the  branch  of  fruit 
much  as  a  sail  propels  a  boat.  The  curving  of  the  edges 
of  the  bract  toward  the  fruit  enables  the  wind  to  catch  it 
all  the  better,  and  to  lift  it  more  or  less  from  the  snow. 
With  changes  in  the  direction  of  the  wind,  there  is  an 
opportunity  for  the  fruit  of  a  single  tree,  if  not  too  much 
crowded  by  others,  to  spread  m  all  directions.  After 
watching  these  maneuvers,  no  one  could  doubt  the  object 
of  the  bent  bracts  of  the  basswood,  and  as  these  vary 
much  in  length  and  width  and  shape  on  different  trees,  it 
would  seem  that  perhaps  nature  is  still  experimenting 
with  a  view  to  finding  the  most  perfect  structure  for  the 
purpose. 

About  one  hundred  and  thirty  paces  west  of  the  house  in 
which  I  live  stand  two  birch  trees.  One  windy  winter 
day  I  made  some  fresh  tracks  in  the  snow  near  my  house, 
and  within  a  few  minutes  the  cavities  looked  as  though 
some  one  had  sprinkled  wheat  bran  in  them,  on  account 
of  the  many  birch  seeds  there  accumulated. 

Other  fruits  in  winter  can  be  experimented  with,  such 
as  that  of  box  elder,  black  ash,  birches,  tulip  tree,  button- 
wood,  ironwood,  blue  beech,  and   occasionally  a  maple. 

22.  Buttonwood  balls.  —  Nature  seems  to  have  no  end 
of  devices  for  sowing  seeds  to  advantage.  Here  is  one 
which  always  interests  me.  The  fruit  of  the  buttonwood, 
or  sycamore,  which  grows  along  streams,  is  in  the  form 
of  balls  an  inch  and  a  half  in  diameter.     These  balls 


40 


SEED  DISPERSAL. 


grow  on  the  tops  of  the  highest  branches,  and  hold  on 
into  winter  or  longer.     The  stems  are  about  two  inches 

long,  and  soon  after  drying, 
through  the  action  of  the 
winds,  they  become  very 
flexible,  each  resembling  a 
cluster  of  tough  strings.  The 
slightest  breeze  moves  them, 
and  they  bob  around  against 
each  other  and  the  small 
branches  in  an  odd  sort  of 
way.  After  so  much  threshing 
I////  ^11      W\Wf      ^■'^^^  they  can  hold  no  longer, 

the  little  nuts  become  loosened 
and  begin  to  drop  oif  a  few  at 
a  time.  Certain  birds  eat  a 
few  and  loosen  others,  which 
escape.  The  illustration  shows 
some  of  these  nuts,  each  sup- 
plied with  a  ring  of  bristles 
about  the  base,  which  acts  as 
a  parachute  to  permit  the  wind 
the  easier  to  carry  them  for 

FIG   29. -(a)  Lax  stem,  supporting  (?/.  g^j-^-^g     dlstaUCC     beforC    falHuo;, 

iruit  of    the  buttonwood,  or  syea-  O" 

more;  (c)   a  single  fruit  separated,  Or  tO   drift  them  OU  tllC  SUrfaCC 

ready  for  the  wind  or  water.  „ 

01  the  snow  or  ice. 
23.   Seeds  that  tempt  the  wind  by  spreading  their  sails. 
—  On  low  lands  in  the  cool,  temperate  climate  of  Europe, 


SEEDS  TRANSPORTED  BY  WTND. 


41 


Asia,  and  North  America,  is  a  common  plant  here  known 
as  great  willow-herb,  a  kind  of  fireweed  [Epilohiian 
august Ifolluni).  There  are  several  kinds  of  fireweeds. 
This  one  gi'ows  from  three  to  five  feet  high,  and  bears 
pretty  pink  flowers.  In  mellow  soil 
the  slender  rootstocks  spread  exten- 
sively, and  each  year  new  s^n-outs 
spring  up  all  around,  six  to  eight  feet 
distant.  Below  each  flower  ripens  a 
long,  slender  pod,  which  splits  open 
from  the  top  into  four  parts,  that 
slowly  curve  away  from  a  central  col- 
umn. The  apex  of  each  seed  is  pro- 
vided with  a  cluster  of  white  silky 
hairs  nearly  half  an  inch  long. 

The  tijDs  of  the  hairs  stick  slightly 
to  the  inside  of  the  recurved  valves, 
some  hairs  to  one  valve,  and  often 
others  to  the  adjacent  valve,  thus 
sjDreading  them  apart  with  the  seed 
suspended  between.  Four  rows  of  the 
seeds  are  thus  held  out  at  one  time. 
Often  not  over  half,  or  even  a  tenth 
part,  of  the  seeds  are  well  developed,  yet 
the  silky  hairs  are  present  and  float  away  in  clusters,  thus 
helping  to  buoy  those  that  are  heavy.  This  is  a  capital 
scheme,  for  when  the  pods  are  dry  and  unfurled,  they 
silently  indicate  to  the  slightest  breath  of  air  that  they 


!.  30.  —  Fruit  of  willow- 
lierb  exposing  seeds  for 
distribution  by  the  wind. 


42 


SEED  DISPERSAL. 


are  ready  for  a  flight,  and  it  does  n't  take  much  to  carry 
them  for  a  long  distance.  As  an  active  boy  delights  to 
venture  again  and  again  over  thin  ice  on  a  shallow  pond 
in  the  pasture,  half  fearing,  yet  half  hoping,  that  he  may 
become  a  hero  by  breaking  through  and  escaping,  so  like- 
wise many  of  these  seeds  and 
seed-like  fruits  spread  them- 
selves out,  as  if  to  tempt  the 
wind  to  come  along  and  attack 
them. 

The  twin  fruits  of  the  pars- 
nip and  some  of  its  near 
relatives  are  light  and  thin 
and  split  aj)art,  each  holding 
on  lightly  to  the  top  of  a 
slender  stem.  In  this  position 
they  are  sure  to  be  torn  off  sooner  or  later.  Somewhat 
after  the  manner  of  the  willow-herb  behave  the  pods  and 
seeds  of  willows,  poplars,  milkweeds,  Indian  hemp,  and 
cotton. 

24.  Why  are  some  seeds  so  small?  —  Do  you  know  why 
so  many  kinds  of  plants  produce  very  small  and  light 
seeds  ?  Would  it  not  be  better  if  they  produced  fewer 
and  larger  seeds,  which  would  then  be  stronger  and  better 
able  to  grow  under  adverse  conditions?  But  a  large 
number  of  small  seeds  cost  the  plant  no  more  effort  than 
a  small  number  of  large  ones,  and  the  lighter  and  smaller 
the  seeds  and  the  more  there  are  of  them,  the  better  their 


Fig.  31.  —Dry  twin  fruits  of  the  parsnip 
held  by  slender  stems  ready  to  be 
blown  away.     (Much  enlarged.) 


SEEDS  TRANSFOETED  BY  liJW.  43 

chances  for  distribution,  especially  for  long  distances. 
The  minute  size  of  spores  of  most  of  the  fungi  are 
given  as  reasons  why  so'  many  of  them  are  so  widely 
distributed. 

Why  is  a  boy  or  man  of  light  weight  chosen  to  ride  the 
horse  on  the  race  track  ?  That  the  animal  may  have  less 
weight  to  carry  and  thereby  use  his  surplus  strength  in 
making  better  time.  The  less  weight  the  parachute  of 
the  seed  of  the  willow-herb  has  to  carry,  the  greater  the 
chances  for  success  in  making  a  long  journey.  Of  the 
willow-herb  it  takes  one  hundred  seeds  to  weio-h  a  milli- 
gram,  including  the  hairs  attached  to  them,  and  it  would 
take  thirty  thousand  to  weigh  as  much  as  an  ordinary 
white  bean. 

25.  Seeds  with  parachutes.  — Many  years  ago  large  por- 
tions of  Huron  and  Sanilac  counties  of  eastern  Michigan 
were  swept  by  a  fire  so  severe  that  the  timber  was  all 
killed.  Fifteen  years  later  the  woody  growth  consisted 
mostly  of  willows,  poplars,  and  birches.  The  seeds  of  all 
kinds  of  willows  and  poplars  are  very  light,  and  are  pro- 
duced in  immense  quantities.  Like  those  of  the  great 
willow-herb,  they  are  beautifully  constructed  for  making 
long  journeys  through  the  air  —  a  fact  that  explains  the 
frequency  of  these  trees  in  burned  districts.  A  consider- 
able number  of  seeds  and  fruits  grow  with  a  parachute 
attached  at  one  end,  not  to  prevent  injury  by  falling 
from  the  tree  top,  but  to  enable  the  wind  to  sustain  and 
transport  them  for  a  longer  distance. 


44 


SEED  DISPERSAL. 


26.  A  study  of  the  dandelion.  —  In  spring  the  dandelion 
is  almost  everywhere  to  be  found ;  every  one  knows  it  — 
the  child  to  admire,  the  gardener  to  despise.  From  each 
cluster  of  leaves  S]oreading  flat  in  the  grass  come  forth 
several  hollow  stems,  short  or  tall,  depending  on  the 
amount  of  sunshine  and  shade.  Each  stem  bears,  not  one 
flower,  but  a  hundred  or  more  small  ones.     Around  and 


Fig.  32.  — Heads  of  the  dandelion  in  fruit,  closed  and  open. 

beneath  each  yellow  cluster  are  two  rows  of  thin,  green, 
smooth  scales  (involucre). 

The  short  outer  row  soon  curls  back,  as  though  for 
rest  or  ornament,  or  for  watching  the  progress  of  the 
colony  above  ;  but  the  inner  row  has  a  very  important 
duty  yet  to  perform  in  guarding  the  large  family  within. 
At  night,  or  in  daytime,  if  the  day  be  wet,  the  long 
scales   press   like    a  blanket  closely  about   the    flowers, 


SEEDS  TRANSPORTED  BY  WIND.  46 

and  do  not  permit  them  to  come  out ;  but  when  the 
sun  is  bright,  it  shrinks  the  outer  side  of  these  scales, 
Avhieh  then  curl  apart,  leaving  the  yellow  flowers  ready 
for  bees  to  visit  or  boys  to  admire  and  study.  For  several 
days  the  flowers  of  a  head  blossom  in  succession,  each 
night  to  be  snugly  wrapped  by  the  scales,  and  the  next 
day  to  be  again  left  open,  if  the  weather  be  fine.  After 
each  flower  in  turn  has  been  allowed  to  see  the  light,  and 
after  all  have  been  crawled  over  by  bee  and  wasp  to  dis- 
tribute the  yellow  pollen  that  seeds  may  be  produced, 
there  is  nothing  else  to  do  but  patiently  wait  for  a  week 
or  two  while  receiving  food  from  the  mother  plant  to 
perfect  each  little  fruit  and  seed.  During  all  this  period 
of  maturing,  day  and  night,  rain  or  shine,  the  scales  hold 
the  cluster  closely ;  the  stem  bends  over  to  one  side,  and 
the  rain  and  dew  is  kept  from  entering.  After  a  while, 
on  some  bright  morning,  the  dandelion  stalk  is  seen 
standing  erect  again,  and  is  probably  surrounded  by  many 
others  in  a  similar  position.  The  dry  air  shrinks  the 
outside  of  the  scales,  and  they  turn  downward ;  the  circle 
of  feathers  at  the  top  of  the  slender  support  attached 
to  the  seed-like  fruit  below  spreads  out,  and  the  com- 
munity, which  now  looks  like  a  white  ball  of  down,  is 
ready  for  a  breeze.  The  feathery  top  is  now  ready  to 
act  as  a  parachute,  and  invites  the  wind  to  catch  up  tlie 
whole  and  float  it  away.  If  there  is  no  breeze,  the  moist 
air  of  night  closes  the  outer  scales ;  each  of  the  feathery 
tips  closes,  and  all  are  secure  till  the  next  bright  day. 


46 


SEED  DISPERSAL. 


Of  a  like  nature  are  fruits  of  thistles,  fireweed,  prickly 
lettuce,  sow  thistles,  scabiosa,  valerian,  cat-tail  flag,  cotton 
grass,  some  anemones,  smoke  tree,  virgin's  bower,  and 
some  of  the  grasses. 

27.  How  the  lily  sows  its  seeds.  — Ripened  pods  of  lilies 
usually  stand  straight  up  on  a  stiff,  elastic  stem ;  begin- 


FiG.  33.  —  At  the  left  a  dry  fruit  of  a  lily  opening  to  permit  seeds  to  dry  and  the  wind 
to  enter ;  to  the  right,  a  fruit  later  in  the  season.    Two  views  of  a  flat  seed. 

ning  at  the  top,  each  one  slowly  splits  into  three  parts, 
which  gradually  separate  from  each  other.  Why  do  they 
not  burst  open  all  of  a  sudden,  like  pea  pods,  and  shoot 
the  seeds  all  about  and  have  the  job  done  with  ?  Or  why 
does  not  the  pod  burst  open  at  the  lower  end  first,  instead 
of  the  upper? 

Observe  that  the  three  opening  cells  are  lashed  together 
loosely  with  a  latticework.      No  slight   breeze  can  dis- 


SEEDS  TRANSFORTED  BY  WIND.  47 

lodge  tlie  seeds,  but  just  see  how  they  behave  in  a  good 
gale !     The   elastic    stems  are  swayed    back   and   forth 
against  each  other,   and  some  of  the   upper   seeds   are 
tossed  out  by  the  wind  that  passes  through  the  lattice, 
and  at  such  times  are  often  carried  to  some  distance. 
The  seeds  at  the  top  having  escaped,  the  dry  pods  split 
down  farther  and  still  farther  and  open  still  wider,  till 
the  bottom  is  reached.     As  the  seeds  are  not  all  carried 
away  the  first  or  even  the  second  time,  and  as  succeeding 
breezes  may  come  from   different   directions,   it  is  thus 
possible  for  the  lily  to  scatter  its  seeds  in  all  directions. 
The  seeds  of  the  lily  are  fiat,  very  thin,  and     ^^y-y.^.^„ 
rather  light,  not  designed  to  be  shot  out  like      |!y!r r  [,Jj|« 
bullets,  but  to  be  carried  a  little  way  by  the     |'  (  l|  l,||| 
wind  ;  the  pods  are  erect,  and  open  at  the  top,     M\  j*  mM 
that  the  seeds  need  not  escape  when  there  is      ^^l/W 
no  wind  or  unless  some  animal  gives  the  stem         ^M 
a  strong  shake.     The  latticework  was  made  ^^ 

for  a  purpose,  and  the  gradual  opening  of  the  tfjl 

pods  prevents  the  supply  from  all  going  in  ^■ 

one  direction  or  in  one  day,  for  a  better  day  fp 

may  arrive.     The  student  will  look  for  and  ^* 

*^  Fig.  34.  Hipe 

compare  the  following  :    Iris,  figwort,    wild     pod  of  poppy  on 

,     1  ,  ,  .  •  1  au   erect,   stiff 

yam,  catalpa,  trumpet-creeper,  centauria,  mul-     stem,  ready  for 
leins,  foxfflove,  beardtonarue,  and  many  other     '''"*?  °''  *"'"'*' 

'  O  '  o       ^  J  to  shake  out  a 

fruits.  ^^^^  seeds   at 

the  top. 

28.    Large  pods  with  small  seeds  to  escape 
from  small  holes.  — The  large  ripe  pod  of  the  poppy  stands 


48 


SEED  DISPERSAL. 


erect  on  a  stiff  stem,  with  a  number  of  small  openings 
near  the  top.  The  seeds  are  nearly 
spherical,  and  escape,  a  few  at  a  time, 
when  the  stem  is  shaken  by  the  wind 
or  some  animal,  thus  holding  a  reserve 
for  a  change  of  conditions.  Here  is 
an  illustration  of  ripe  pods  of  a  bell- 
flower,  Camjjanula  turhinata,  nodding 
instead  of  erect. 

The  small  holes  are  still 
uppermost,  but  to  be  upper- 
most in  this  case  it  is  neces- 
sary for  them  to  be  at  the 
base  of  the  pod. 

29.  Seeds  kept  dry  by  an 
umbrella  growing  over  them. 
—  When  mature,  the  apple 
of  Peru,  Nicandra,  keeps 
every  dry  bursting  fruit 
covered  with  a  hood,  um- 
brella,   or    shed,    so    that 


Fig.  35.  — Ripe  pods  of  bellflower  bent  over  ;  the 

holes  opening  when  dry  to  allow  seeds  to  be    seeds     may     bc      kcpt     COU" 
shaken  out.  ,  •  t  i         t  i  i 

tmually  dry  and  may  be 
spread  with  every  shake  by  the  wind,  or  by  an  animal, 
in  rainy  weather  as  well  as  in  dry. 

In  the  words  of  Dr.  Gray,  "The  fruit  is  a  globular 
dry  berry,  enclosed  by  a  five-parted,  bladdery  inflated 
calyx."      The   margins  of   the   lobes   of   the  calyx  curl 


SEEDS  TliAXSPORTED  BY  WIND. 


49 


upwards  and  outwards  as  the  berry  hangs  with  the  apex 
downward. 

The  berry  is  as  hirge  as  one's  thumb,  and  when  ri})e, 
bursts  open  irregularly  on  the  upper  side  as  it  hangs  up 
under  the  calyx.  As  the  covering  of  the  pod  opens  more 
and  more,  a  few  seeds  at  a  time  may  be  rattled  out  by 
wind  or  animal.     The  numerous  large  and  light  fruits, 


Fig.  37.  — The  same 
E^G.  36.  —  Mature  fruit  of  apple  of  Peru  with  the   calyx 

covered  by  an  enlarged  calyx.  removed. 


Fig.  38.  —  The  same  as 
Fig.  37,  except  that 
it  is  older  and  some- 
what changed. 


with  calyx  surrounding  them,  are  each  supported  on  a 
nodding  stem,  stiff  and  elastic,  which  gives  the  wind  a 
good  chance  to  sway  them  about.  Water  does  not  seem 
to  get  into  the  berries  even  when  they  are  torn  open, 
for  when  it  is  poured  over  the  branches  it  rolls  off  tlie 
calj'x  roof  as  freely  as  from  a  duck's  back.  The  fruits 
of  Physalis  are  apparently  kept  dry  in  a  manner  similar 
to  the  apple  of  Peru,  although  when  first  mature  they  are 
soft  and  juicy,  considerably  like  a  ripe  tomato. 


50 


SEED  DISPERSAL. 


30.  Shot  off  by  wind  or  animal.  —  The  calyx  of  sage, 
bergamot,  and  most  other  mints,  remains  dry  and  stiff,  as 
a  cup  to  hold  one  to  four  little  round  nutlets  as  they 
ripen.  The  figure  shows  two  of  these  in  section,  as  they 
are  attached  to  the  main  stem  of  the  plant,  or  one  of  its 

branches.  Observe  the  di- 
rection taken  by  the  upper 
and  by  the  lower  points  of 
the  calyx.  When  dry,  the 
plant  behaves  somewhat  as 
follows:  when  the  wind 
jostles  the  branches  against 
each  other,  or  when  an  ani- 
mal of  some  kind  hits  the 
plant,  this  movement  causes 
many  of  these  cups  to  get 

Fig.  39. -Ripe  calyx  of  sage,  first  as  iiuslied     CaUgllt ;    but  tllC  clastlc  Stcm 
down ;  second  as  let  loose  throwing  nutlets.  i  i        -i        -i         -,       ,         • , 

comes  suddenly  back  to  its 
place,  and  in  so  doing  flips  a  nutlet  or  more  from  its 
mouth  one  to  six  feet,  somewhat  as  a  boy  would  flip  a 
pea  with  a  pea-shooter.  In  our  garden,  July  2,  when 
plants  of  sage.  Salvia  interrupta,  were  ripening  their 
fruit,  we  found  it  difficult  to  collect  any  seeds,  but 
seedlings  were  observed  in  abundance  on  every  side  of 
the  plant,  some  to  the  distance  of  six  feet.  Plants  dis- 
persing seeds  in  this  manner  have  been  called  catapult 
fruits.  Examine  ripening  fruits  of  blue  curls,  pennyroyal, 
germander,  balm,  horehound,  dittany,  hyssop,  basil,  mar- 


SEEDS   TRANSPOBTED   BY  WIND.  61 

joram,  thyme,  savory,  catmint,  skullcap,  self-heal,  dragon's 
head,  motherwort,  and  various  dry  fruits  of  several 
chickweeds. 

31.  Seed-like  fruits  moved  about  by  twisting  awns.  — 
Most  of  the  grains  of  grasses  are  invested  with  glumes, 
or  chaff,  and  a  considerable  per  cent  of  the  chaff  has 
awns,  some  of  which  are  well  developed  and  some  poorly 
developed.  The  distribution  of  such  grasses  depends  on 
several  agents  —  wind,  water,  and  animals.  The  chaff  and 
awns  of  all  are  hygroscopic ;  that  is,  are  changed  by  dif- 
ferences caused  by  variation  of  moisture  in  the  air.  Sweet 
vernal  grass,  tall  oat  grass,  holy  grass,,  redtop,  animated 
or  wild  oats,  blue-joint,  and  porcupine  grass  are  among 
them.  When  mature,  the  grain  and  glumes  drop  off,  or 
are  pushed  off,  and  go  to  the  ground.  When  moist,  these 
awns  untwist  and  straighten  out,  but  when  dry  they  coil 
up  again ;  with  each  change  they  seem  to  crawl  aljout  on 
the  ground  and  work  down  to  low  places  or  get  into  all 
sorts  of  cracks  and  crevices,  where  the  first  rain  is  likely 
to  cov;er  them  more  or  less  with  earth,  after  which  they 
are  ready  for  growth. 

32.  Grains  that  bore  into  sheep  or  dogs  or  the  sand. — 
Porcupine  grass,  St'qja  sjmrtea,  grows  in  dry  soil  in  the 
northern  states,  but  more  particularly  on  the  dry  prairies 
of  the  central  portion  of  the  United  States.  This  grass, 
when  ripe,  has  a  very  bad  reputation  among  ranchmen 
for  the  annoyance  the  bearded  grain  causes  them.  The 
grains  are  blown  into  the  stubble  among  grasses  with  the 


52  SEED   DISPERSAL. 

bearded  point  down,  sticking  into  the  soil.  The  first  rain 
or  heavy  dew  straightens  out  the  awns,  which  are  twisted 
again  as  they  dry.  The  bearded  point  works  a  little 
farther  with  each  change,  and  after  twisting  and  untwist- 
ing a  number  of  times  it  gets 
down  three  or  four  inches  into  the 
sand,   often  to   moisture,  where 


Fig.  40.  —  Ripe  fruit  of  pin       .i  -,  i      ,i 

clover,  or  Aifiieriiia,    the  awus   dccay  and   the  gram 
ready  to  twist  into  fleeces    germiuates.      Hcre  is  an  admi- 

of  sheep  or  into  loose  soil.       o 

rable  scheme  for  moving  about 
and  for  boring  into  the  ground.  But  this  is  not  all. 
The  grains  are  quick  to  catch  fast  to  clothing,  as 
people  move  among  the  plants,  and  they  are  ad- 
mirably fitted  for  attaching  themselves  to  dogs  and 
sheep,  which  they  annoy  very  much.  These  animals 
transport  the  grains  for  long  distances.  The  twist- 
ing and  untwisting  of  the  awns  enable  the  grain  to 
bore  through  the  fleeces,  and  even  to  penetrate  the  skins 
and  make  wounds  which  sometimes  cause  the  death  of  the 
animal.  Examine  also  seeds  of  pin  clover,  Alfilerilla, 
which  is  becoming  abundant  in  many  parts  of  the  world. 
33.  Winged  fruits  and  seeds  fall  with  a  whirl.  —  The 
large  fruit  of  the  silver  maple  falls  in  summer.  As  these 
trees  are  most  abundant  along  the  margins  of  streams, 
the  fruit  often  drops  into  the  water  and  is  carried  down 
stream  to  some  sand  drift  or  into  the  mud,  where  more 
sand  is  likely  to  cover  them.  Thus  sown  and  planted 
and  watered,  they  soon  grow  and  new  trees  spring  up. 


SEEDS   TRANSPORTED   RY   WIND. 


53 


But  in  many  instances  a  strong  breeze,  sometimes  a 
whirlwind,  has  been  seen  to  carry  these  mature  fruits 
from  the  tree  to  a  distance  of  thirty  rods. 

A  thin  sheet  of  paper  descends  more  slowly  than  the 
same  material  put  in  the  form  of  a  ball.  On  the  same 
principle,  many  seeds  and  fruits  are  flattened, 
apparently  for  a  purpose ;  not  that  they  may 
be  easily  shot  through  the  air  by  some  elastic 
force,  not  to  increase  their  chances  for  attach- 
ment to  animals,  but  to  enable  the  wind  to 
sustain  them  the  longer  and  carry  them  farther. 
Some  seeds  and  dry  fruits  are  said  to  have 
wings,   with   the    general   understanding   that 

ir^^  they  are  by  this  means  better  fitted 

i\M\       ^^  ^^^  sustained  in  air.     We  shall 
find  that  all  or  nearly  all  flattened 
seeds  and  dry  fruits,  also  w^inged 
seeds  and  fruits,  are   one-sided,   unbalanced, 
and    more  or  less  twisted ;    consequently,  in 
falling  to  the  ground  they  whirl  about,  and 
are  thus  kept  much  longer  in  the  air  than 
they  would  be  if  shaped  more  like  a  winged 
arrow.     Even  the  wings  on  the  fruit  of  some 
of  the  ashes  are  twisted,  though  mam*  of  them 
are  flat.     Experiments  with  these  things  are 
whirl  about    sure  to  interest  inquisitive  children,  or  even 
.1  ing.     QJ^g^.  persons,  when  once  started  right ;  they 
are  likely  to  prove  as  interesting  as  flying  kites,  skating, 


Fig.  41.  — Sin- 
gle fruit  of 
silver  maple. 


Fig.  42. 

Winged  seed  of 

pine.   Want  of 

symmetry 

causes  it  to 


54  SEED  DISPERSAL. 

fishing,  or  coasting  on  the  hillside.  Try  experiments  with 
seeds  of  catalpa,  trumpet-creeper,  wild  yam,  pine,  spruce, 
arbor  vitse,  and  fruits  of  maple,  box  elder,  birch,  hop  tree, 
blue  beech,  ailanthus,  ash,  tulip  tree,  —  in  fact,  anything 
of  this  nature  you  can  find,  whether  the  name  is  familiar 
or  not.  No  two  of  them  will  behave  in  all  respects  alike. 
34.  Plants  which  preserve  a  portion  of  their  seeds  for  an 
emergency.  —  Many  a  great  general  or  business  man  has 
learned  by  experience  and  observation  that  it  is  usually 
unwise  to  exhaust  all  resources  in  one  effort.  If  possible, 
he  always  plans  to  have  something  in  reserve  for  an 
emergency  —  a  loophole  for  escape  from  difficulty.  We 
have  seen  in  many  instances  that  plants  are  endowed 
with  the  same  trait.  This  is  well  illustrated  by  the  way 
in  which  the  jack-pine,  Pinus  [^Bcoiksiancc]  divaricata, 
holds  in  reserve  a  portion  of  its  seeds,  to  be  used  in  case 
the  parent  trees  are  killed  by  fire.  In  1888  I  made  a 
study  of  this  tree  as  it  lives  on  the  sandy  plains  of 
Michigan.  The  tree  is  often  killed  by  fire,  and  never" 
sprouts  from  the  stump,  as  do  oaks,  willows,  cherries,  and 
most  other  trees.  The  jack-pine  grows  readily  and  rapidly 
from  seed  dropped  on  the  sand,  and  begins  to  bear  cones 
and  seeds  in  abundance  while  it  is  yet  only  a  few  years 
old,  perhaps  as  young  as  five  years  in  some  instances. 
The  cones  open  slowly  to  liberate  their  seeds,  some  of 
them  only  after  months  or  even  years,  and  in  some  cases 
they  never  open  at  all.  I  have  seen  cones  containing 
good  seeds  that  had  been  nearly  grown  over  by  the  tree. 


SEEDS  TRANSPORTED  BY  WIND. 


65 


Dry  weather,  the  dryer  and  hotter  the  better,  causes  many 
of  these  stubborn  old  cones  to  open  their  scales  and  allow 
the  seeds  to  escape.  What  can  be  the  advantage  in  cones 
of  this  nature  ?  Let  us  see.  A  brisk  fire  passes  over  the 
ground  at  irregular  intervals,  usually  of  from  one  to  ten 
years;  it  licks  up  all  dry  leaves  and  sticks,  and  kills  the 


Fig.  43. — Cone  of  jack-pine  closely 
covering  its  seeds,  often  for  sev- 
eral years. 


Fig.  44.  —  Cone  of  jack-pine  as  opened 
by  heat,  sowing  seeds. 


pine  trees  and  all  else  above  ground.  The  soil  and  the 
trunks  of  trees  are  blackened,  and  by  lack  of  reflection 
the  heat  of  the  sun  is  rendered  more  intense ;  besides,  the 
heat  of  the  fire  acts  slowly  on  the  unburned  cones  as  they 
are  left. on  the  dead  trees.  By  the  time  the  quick  hot 
fire  has  passed  over,  the  cones  have  slowly  opened  and 
begun  scattering  seeds  on  the  vacant  and  newly  burned 
ground,  at  a  time  when  there  is  the  best  possible  chance 
for  them  to  grow.    I  picked  a  few  unopened  cones  which, 


56  SEED  DISPERSAL. 

according  to  my  judgment,  were  from  two  to  four  years 
old.  They  were  placed  under  glass  in  a  dark  sheet-iron 
dish  and  exposed  to  the  sun.  The  extra  heat  caused  the 
cones  to  open ;  many  seeds  were  obtained  and  sown,  and 
in  five  days  they  began  to  come  up,  95  per  cent  germinat- 
ing. From  the  same  tree  I  selected  at  the  same  time 
older  cones,  which  I  believe  to  be  from  four  to  six  years 
old  at  least.  From  these,  225  seeds  were  sown,  191  of 
which  germinated  —  about  85  per  cent. 


CHAPTER    VI. 


PLANTS   THAT   SHOOT   OFF   THEIR   SPORES   OR   SEEDS. 


By  numerous  devices  a  large  number  of  the  lower  plants 
send  ott"  their  ripe  spores  with  considerable  force.  Some 
call  them  sling  fruits.  One 
in  particular,  Piloholus  cris- 
taUimiSy  found  about  damp 
stables,  I  have  observed  to 
shoot  black  masses  of  spores 
to  a  spot  on  a  wall  six  feet 
above  the  ground,  with 
enousrh  force  to  have  carried 
them  not  less  than  twelve 
feet.  When  ripe  and  dry, 
the  spores  of  most  ferns  are 
shot  from  the  parent  plant 
by  a  motion  forcible  enough 
not  only  to  burst  the  sporan- 


gium, 


the    vessel    that    con- 


tains the  spores,  but  also  to 
turn  it  inside  out. 

35.  Dry  pods  twist  as  they 
split  open  and  throw  the  seeds. 
—  In  December,  while  absent  from  home,  T  collected  for 


Fig.  45.  —  Spores  of  Pilolinlux  before  and 
while  shooting  its  spores. 


58  SEED  DISPERSAL. 

future  study  some  pods  of  the  Chinese  wistaria,  and  left 
them  on  my  desk  in  the  library  for  the  night.  The  house 
was  heated  by  a  hot-air  furnace.  In  the  morning  the 
pods  were  in  great  confusion ;  most  of  them  had  split 
and  curled  up,  and  the  seeds  were  scattered  all  about  the 
room.  As  usual  the  little  daughter,  an  only  child,  was 
accused  of  spoiling  my  specimens,  but  she  showed  her 
innocence.  A  little  investigation  and  a  few  experiments 
with  some  pods  net  yet  opened  explained  the  whole 
matter  satisfactorily.  The  stout  pods  grow  and  ripen  in 
a  highly  strained  condition,  with  a  strong  tendency  to 
burst  spirally,  the  two  half-pods  being  ready  to  coil  and 
spring  in  opposite  directions;  when  the  valves  can  no 
longer  hold  together,  they  snap  with  a  sharp  noise  and 
sling  the  heavy  seeds,  giving  them  a  good  send-off  into 
the  world.  As  a  pair  of  birds  build  a  nest,  hatch  eggs, 
rear  their  young,  and  then  send  them  forth  to  seek  their 
fortunes,  so  for  months  the  mother  plant  had  labored, 
had  produced  and  matured  seeds,  which  at  last  it  scat- 
tered broadcast.  Goethe,  Kerner  von  Marilaun,  each  in- 
dependently, and  very  likely  others,  had  an  experience 
with  ripe  pods  brought  to  a  warm  room  very  similar 
to  my  own.  In  many  cases  the  ripe  and  drying  fruits 
are  "  touched  off "  by  wind  jostling  the  branches  or 
by  animals  passing  among  them ;  in  the  latter  case 
there  is  a  chance  that  a  portion  of  the  discharges  will 
be  lodged  somewhere  on  the  animal  and  be  carried 
along  with  it. 


PLANTS  THAT  SHOOT   TJI  EI  It  SEEDS. 


59 


36.  A  seed  case  that  tears  itself  from  its  moorings.  —  The 
perennial  phlox  in  cultivation  distributes  its  seeds  in  the 
following  manner:  when  ripe,  the  calyx  becomes  dry 
and  paper-like,  and  spreads  out  in  the  form  of  a  saucer. 
The  thick-walled  dry  pistil  opens  from  the  top  into  three 


Fig.  47.  —  Fruit  of  violet  partially 
dried  and  split  into  three  pieces, 
each  piece  pinching  the  seeds  so 
closely  that  sooner  or  later  all  are 
thrown  out. 

pieces  with  a  snap,  spread- 
ing open  so  far  against  the 

Fig.  46.-  a  dry  pod  of  wil.l  bean  bursting        calvX   that  it  is   tom  from 
spirally  to  throw  the  seeds.  ^ 

the  brittle  attachment  ; 
away  go  the  seeds,  mingled  with  the  fragments  of  the 
pistil,  no  longer  of  any  use. 

Fruits  that  sling  their  seeds  are  to  be  found  in  every 
neighborhood,  and  are  first-class  objects  for  the  curious 
person  to  see  and  handle.  Very  fortunate  is  the  girl  or 
boy  w'ho  is  never  fully  satisfied  with  what  he  reads  and 
sees  pictured,  but  has  a  strong  desire  to  learn  how  plants 


60 


SEED  DISPERSAL. 


are  made  and  how  they  behave.  A  considerable  number 
of  seed  pods  have  been  ilkistrated  with  notes  in  recent 
schoolbooks.  Here  are  some  of  them  : 
peas  and  vetches,  and  some  kinds  of 
beans,  violets,  balsams,  wood  sorrel, 
geranium,  castor  bean,  some  of  the 
mustards  and  cresses  and  their  cousins, 
Allilerilhi,  richweed,  Pilea,  witch-hazel, 
and  others.  Each  of  those  will  well 
repay  study,  especially  the  fruit  and 
seeds  of  oxalis.  The  witch-hazel  bears 
a  hard,  woody,  nut-like  fruit,  as  large  as 
a  hazelnut ;  when  ripe,  the  apex  gaps 
open  more  and  more,  the  sides  pressing 
harder  against  each  smooth  seed,  till 
finally  it  is  shot,  sometimes  for  a  dis- 
tance of  thirty  feet.  The  girl  who  has 
shot  an  apple  seed  or  lemon  seed  with 
pressure  of  thumb  and  finger  across  a  small  room,  can 
understand  the  force  needed  to  shoot  a  seed  but  little 
heavier  than  that  of  the  apple  two  or  three  times  that 
distance. 


Fig.  48.— Dry  fruit  of  witch 
hazel  shooting  seeds. 


CHAPTER   VII. 

PLANTS    THAT    AKE    CARRIED   BY   ANIMALS. 

With  the  frosts  of  autumn  ripe  acorns,  beechnuts,  bit- 
ternuts,  butternuts,  chestnuts,  hickory  nuts,  hazelnuts,  and 
walnuts  are  severed  from  the  parent  bush  or  tree  and  fall 
to  the  ground  among  the  leaves. 

37.  Squirrels  leave  nuts  in  queer  places  and  plant  some  of 
them.  —  Even  before  the  arrival  of  frosts  many  of  these 
are  dropped  by  the  aid  of  squirrels,  gray  and  red,  vi^hich 
cut  the  stems  with  their  teeth.  The  leaves,  with  the  help 
of  the  shifting  winds,  gently  cover  the  fruit,  or  some 
portions  of  it,  and  make  the  best  kind  of  protection  from 
dry  air  and  severe  cold ;  and  they  come  just  in  the  nick 
of  time.  Dame  Nature  is  generous.  She  produces  an 
abundance ;  enough  to  seed  the  earth  and  enough  to  feed 
the  squirrels,  birds,  and  some  other  animals.  The  squirrels 
eat  many  nuts,  but  I  have  seen  them  carry  a  portion  for 
some  distance  in  several  directions,  and  plant  one  or  two 
or  three  in  a  place,  covering  them  well  with  soil.  It 
may  be  the  thought  of  the  squirrel  —  I  cannot  read  his 
thoughts  —  to  return  at  some  future  time  of  need,  as  he 
often  does.  But  in  some  cases  he  forgets  the  locality,  or 
does  not  return  because  he  has  stored  up  more  than  he 
needs ;  or  in  some  cases  the  squirrels  leave  that  locality 


62 


SEED  DISPERSAL. 


or  are  killed ;   in  any  such  case  the  planted  nuts  are  not 
disturbed.    At  all  events,  some  of  the  nuts  —  one  now  and 


Fig.  49.  —  A  black  walnut  as  left  by  a  red  squirrel  on  a  small  oak  tree. 

then  is  all  that  is  needed  —  are  allowed  to  remain  where 
planted.  In  this  way  the  squirrel  is  a  benefit  to  the  trees 
and  pays  for  the  nuts  he  eats.     He  has  not  lived  in  vain, 


PLANTS   THAT  ARE   CARRIED   BY  ANIMALS.      63 

for  he  is  a  tree  planter  and  believes  in  arboriculture.  His 
arbor  day  comes  in  autumn,  and  he  needs  no  message  from 
the  governor  to  stimulate  him  to  work. 

After  some  red  squirrels  had  been  given  black  walnuts, 
a  member  of  my  family  saw  them  hide  the  nuts  in  all 
conceivable  places,  and  in  some  instances  place  them 
above  a  cluster  of  small  branches  of  a  tree  for  support 
where  three  or  more  twigs  spread  from  nearly  the  same 
place.  Here  the  nuts,  one  in  a  place,  were  left  till  perhaps 
shaken  to  the  ground  by  a  severe  wind  or  by  some  other 
cause.  In  one  winter,  without  hunting  for  them,  six  to 
ten  places  were  found  in  one  neighborhood  of  Michigan, 
where  something  had  placed  a  single  walnut  or  acorn  in 
the  forks  of  small  branches.  In  some  cases  a  severe  wind 
could  have  dislodged  the  nut. 

On  February  18,  1897,  I  found  a  single  black  walnut 
held  by  small  branches  of  a  red  oak. 

The  oak  was  an  inch  and  a  half  in  diameter,  and  the 
nut  was  about  six  feet  from  the  ground.  The  nearest 
bearing  tree  was  fully  three  hundred  long  steps  distant. 
We  can  imagine  that,  through  fright  or  other  causes, 
a  squirrel  might  be  suddenly  interrupted  while  carrying 
nuts,  and  might  then  drop  them  to  the  ground,  where 
later  a  tree  would  be  started. 

38.  Birds  scatter  nuts.  —  The  work  of  birds  in  scatter- 
ing seeds  and  fruits  has  long  been  recognized.^ 

^  In  the  fall  of  1897,  Prof.  C.  F.  Wheeler  saw  a  blue  jay  fly  from  a  white 
oak  tree  with  an  acorn  in  its  mouth.     The  bird  went  to  the  ground  four  or 


64  SEED  DISPERSAL. 

Some  friends  of  mine  collected  a  quantity  of  hazelnuts, 
while  yet  the  green  husks  enclosed  the  nuts,  and  placed 
them  near  the  house  to  dry.  At  once  they  were  discov- 
ered by  a  blue  jay,  which  picked  out  a  nut  at  a  time,  flew 
away,  held  the  nut  between  its  toes,  cracked  it  from  the 
small  end,  and  ate  the  contents.  In  this  operation  a  num- 
ber of  nuts  sli23ped  away  and  were  lost.  But  it  seems  that 
all  were  not  eaten,  for  the  next  season  half  a  dozen  or  more 
hazel  shoots  came  up,  and  to-day  a  new  patch  of  hazel 
bushes  is  growing  in  the  yard.  Doubtless  many  acorns 
are  carried  from  place  to  place  and  dropped  in  an  aimless 
way  by  woodpeckers,  blue  jays,  and  crows  ;  also  beech- 
nuts by  these  birds,  and  by  nuthatches,  and  by  pigeons, 
before  the  latter  became  nearly  extinct.  Woodpeckers 
and  blue  jays  place  beechnuts  and  small  acorns  in  the 
crevices  of  bark  on  standing  trees.  If  left  there  very 
long,  the  nuts  will  become  too  dry  to  grow,  but  in  the  act 
of  transporting  them  some  of  the  nuts  may  be  accidentally 
dropped  in  various  places. 

39.  Do  birds  digest  all  they  eat  ?  —  To  determine  wli ether 
seeds  would  lose  their  vitality  in  passing  through  the  digest- 
ive organs  of  birds,  Kerner  von  Marilaun  fed  seeds  of  two 
hundred  and  fifty  different  species  of  plants  to  each  of  the 
following  :  blackbird,  song  thrush,  robin,  jackdaw,  raven, 
nutcracker,  goldfinch,  titmouse,  bullfinch,  crossbill,  pigeon, 

five  rods  distant  and  crowded  the  acorn  into  the  soil  as  far  as  it  could,  cover- 
ing the  spot  with  a  few  leaves.  A  member  of  my  family  saw  a  blue  jay 
leave  half  of  a  black  walnut  in  the  forks  of  several  small  branches. 


PLANTS   THAT  ARE    CARRIED   BY  ANIMALS.      65 

fowl,  turkey,  duck,  and  a  few  others  ;  also  to  marmot, 
horse,  ox,  and  pig,  making  five  hundred  and  twenty  sepa- 
rate experiments.  As  to  the  marmot,  horse,  ox,  and  pig, 
almost  all  the  fruits  and  seeds  were  destroyed.  From 
the  ox  grew  a  very  few  seeds  of  millet,  and  from  the  horse 
one  or  two  lentils  and  a  few  oats  ;  from  the  pig  a  species 
of  dogwood,  privet,  mallow,  radish,  and  common  locust. 
Under  ordinary  conditions,  no  seed  was  found  to  germi- 
nate after  passmg  through  the  turkey,  hen,  pigeon,  cross- 
bill, bullfinch,  goldfinch,  nutcracker,  titmouse,  and  the 
duck.  Ravens  and  jackdaws  passed  Avithout  injury  seeds 
of  stone  fruits  and  others  with  very  hard  coats.  Of  seeds 
that  passed  through  the  blackbird  75  per  cent  germinated, 
85  per  cent  in  the  case  of  the  thrush,  80  per  cent  in  the 
case  of  the  rob  in. ^ 

40.  Color,  odor,  and  pleasant  taste  of  fruits  are  advertise- 
ments. —  In  summer,  buds  are  formed  on  l)uslies  of  black 
raspberry,  blossoms  appear,  and  these  are  followed  by 
small,  green,  and  bitter  berries,  which  hardly  anj^thing 
cares  to  eat.  They  grow  slowly,  become  soft  and  pulpy, 
and  finally  good  to  eat.  How  is  bird  or  boy  or  girl  to 
know  where  they  are  and  when  they  are  fit  to  eat  ?  The 
plant  has  enterprise  and  has  displayed  two  want  advertise- 

^  It  should  be  noted  that  the  blackbird  here  mentioned  is  not  the  same 
as  either  of  our  blackbirds,  but  a  thrush  much  like  our  robin  ;  that  the 
robin  mentioned  is  a  ground  warbler  nearly  related  to  our  bluebird.  It 
should  also  be  noted  that  jackdaws,  ravens,  thrushes,  and  probably'  many 
others  eject  thousands  of  seeds  by  the  ruouth  for  one  which  passes  through 
the  intestines. 


66  SEED  DISPERSAL. 

ments  by  painting  the  berries  first  dark  red,  and  then  dark 
purple,  when  they  are  good  to  eat.  But  is  the  phmt  made 
expressly  to  produce  berries,  just  to  feed  birds  and  chil- 
dren ?  If  that  be  all,  why  are  seeds  formed  in  the  berries 
in  such  large  numbers  ?  No  !  They  produce  berries  that 
contain  seeds,  and  from  these  seeds  are  to  grow  more 
bushes.  Then  why  should  not  the  berries  always  remain 
bitter  or  hard,  so  that  nothing  would  touch 
them  ?  If  we  may  say  so,  the  plant  pro- 
duces sweet  and  showy  berries  on  purpose 
to  be  eaten,  that  the  seeds  may  be  carried 
away.  What  becomes  of  the  seeds  ?  Each 
FIG.  50.  -  Raspberry,  ^^^^  is  cuclosed  lu  a  hard,  tough  covering, 
ripened,  picked,  and    which  Drotccts  it  from  dcstructiou  in  the 

ready  to  be  eaten.  ■*• 

.  stomachs  of  many  birds  and  some  other  ani- 
mals. The  seeds  are  well  distributed  by  the  animals  that 
eat  the  berries.  The  brilliant  colors  of  ripe  berries  say  to 
bird  and  child :  "  Here  we  are  ;  eat  us,  for  we  are  good." 
The  sweet  pulp  pftys  the  birds  for  distributing  the  seeds, 
else  they  would  not  be  so  distributed.  The  seeds  are  as 
well  provided  for  locomotion  as  the  ticks,  the  mites,  and 
the  spiders,  and  when  ready  to  go,  the  berries  flaunt  their 
colors  to  attract  attention.  You  see,  then,  that  although 
the  old  parent  bush  cannot  change  its  place,  young  bushes 
grow  from  the  tips  of  the  branches,  and  seedlings  spring 
up  at  long  distances  from  their  old  homes. 

Sparrows,  finches,  and  similar  birds  in  the  winter  eat 
and  destroy  seeds  of  grasses  and  weeds,  while  the  same 


PLANTS   THAT  ARE   CARRIED   BY  ANIMALS.      07 

birds  in  summer  and  autumn  eat  bushels  of  blueberries, 
huckleberries,  elderberries,  raspberries,  strawberries,  and 
similar  fruits,  and  distribute  their  unliarmed  seeds  over 
thousands  of  acres,  which  otherwise  might  never  support 
a  growth  of  these  species. 

The  downy  woodpecker,  among  other  things,  devours 
berries  of  three  kinds  of  dogwood,  Virginia  creeper,  service 
berry,  strawberry,  pokeberry,  poison  ivy,  poison  sumac, 
stag-horn  sumac,  and  blue  beech. 

The  hairy  woodpecker  devours  many  of  the  above  fruits, 
as  well  as  those  of  spicebush,  sour  gum,  cherries,  grapes, 
blackberries.  The  flicker  devours  most  of  the  fruits  listed 
for  the  two  woodpeckers  named  above,  also  hackberry, 
black  alder,  green  brier,  bayberries.  A  number  of  other 
woodpeckers  possess  habits  much  the  same"  as  the  three 
above  named.  The  cedar  bird  devours  many  species  of 
hard-seeded  fruits. 

The  various  shades  of  red  appear  to  good  advantage 
amono;  crreen  leaves.  As  illustrations  of  such,  we  have 
the  wintergreen,  partridge  berry,  bush  cranberry,  bearberry, 
service  berry,  currant,  holly,  strawberry,  red-berried  elder, 
winter  berry,  honeysuckle,  and  many  more.  Where  the 
leaves  are  liable  to  become  red  in  autumn  the  berries  are 
often  blue.  Of  such,  notice  wild  grapes,  blueberries,  and 
berries  of  sassafras,  though  the  flowering  dogwood  has  red 
leaves  as  well  as  red  berries. 

There  is  a  reason  for  prickles  on  rosebushes.  When 
ripe,  rosehips  are  usually  red  or  yellow,  and  thus  attract 


68  SEED  DISPERSAL. 

birds  which  are  fond  of  the  fleshy  portion  outside  ;  but 
tlie  seed-like  nuts  are  too  hard  and  dry  to  suit  their  taste, 
and  are  rejected  and  sown  in  the  vicinit}",  where  the  ripened 
hips  are  picked  in  pieces  and  eaten.  Mice  and  red  squir- 
rels are  also  fond  of  the  seed-like  nutlets  of  roses,  but  sel- 
dom secure  them  from  the  bushes.  Why,  do  you  ask? 
Because  the  prickles  were  most  likely  placed  on  the  rose- 
bushes to  prevent  this  very  thing,  and  not  to  annoy  the 
lover  of  flowers,  or  to  prevent  her  from  cutting  what  she 
needs. 

41.  The  meddlesome  crow  lends  a  hand.  —  "One  of  the 
most  industrious  and  persistent  seed-transporting  agencies 
I  know  of  is  that  ubiquitous,  energetic,  rollicking,  meddle- 
some busybody,  the  crow.  I  have  seen  crows  gather  by 
hundreds  and  have  a  regular  powwow,  a  mass  convention, 
where  they  seemed  to  discuss  measures  and  appoint  officers. 
At  length  they  get  through,  and  as  they  start  to  fly  away 
many,  if  not  all,  will  drop  something.  I  have  found  these 
to  be  acorns,  walnuts,  hickory  nuts,  buckeyes,  sycamore 
balls,  sticks,  eggshells,  pebbles,  etc.  As  a  crow  leaves  an 
oak  he  will  pluck  an  acorn,  which  he  may  carry  five  miles 
and  light  on  a  beech  tree  where  something  else  will  attract 
his  attention,  when  he  will  drop  the  acorn  and  maybe  pluck 
a  pod  of  beechnuts  and  fly  away  somewhere  else." — Prof. 
W.  B.  Barrows. 

The  number  of  seeds  distributed  by  crows  is  enormous, 
and  consists  of  many  species,  including  poison  ivy  and 
poison  sumac,  wild  cherry,  dogwood,  red  cedar,  sour  gum. 


PLANTS   THAT  ARE   CARRIED   BY  ANIMALS.      69 


and  Virginia  creeper.  The  hard,  undigested  seeds  are 
mostly  expelled  from  the  mouth  in  pellets,  shown  in  the 
illustration,  and  germi- 
nate more  promptly  than 
those  untouched  by  birds. 
Bears  are  very  fond  of 
berries,  and  will  scatter 
the  seeds  of  service  ber- 
ries, elder  berries,  choke- 
cherries,  raspberries,  and 
blackberries. 

42.  Ants  distribute 
some  kinds  of  seeds.  — 
Ants  are  numerous, 
strong,  skillful,  and  in 
suitable  w^eather  are  al- 
ways very  busy.  Their 
habits  have  been  investigated,  and  it  has  been  found  that 
in  some  respects  they  are  genuine  farmers  on  a  small 
scale.    They  have  their  slaves  (not  hired  help) ;  they  feed 

their  plant  lice,  remove 
them  from  place  to 
place,  and  otherwise 
care  for  them,  because 
the  lice  constitute  one 
of  the  chief  sources  of 
their  supply  of  sweet.  They  build  roads  and  houses,  and 
enjoy  society  after  their  fashion.      They   have   use   for 


Fig.  51.  — Two  views  of  a  pellet  of  seeds  and  rub- 
bish from  a  crow.  Froin  bulletin  No.  6,  United 
States  Department  of  Agriculture,  Division  of 
Ornithology  iind  Mammology. 


Fig.  52.  —  Seed  of  bloodroot  with  caruncle  or  crest, 
which  serves  as  a  handle  for  ants  to  hold  on  to. 
Ant  ready  to  take  the  seed. 


70  SEED  DISPERSAL. 

certain  kinds  of  seeds,  portions  or  all  of  which  they  eat 
at  once  or  carry  to  their  homes.  A  number  of  persons 
in  different  countries  and  at  different  times  have  seen 
ants  carrying  seeds.  Some  young  student  of  botany  may 
have  noticed  along  one  side  of  the  glossy  seeds  of  the 
bloodroot  a  delicate,  fleshy  ridge,  and  wondered  what 
could  be  its  use.  The  answer  can  now  be  given  with  a 
good  degree  of  confidence.  The  ants  either  eat  this  fleshy 
ridge  at  once,  or,  as  more  frequently  happens,  carry  such 
seeds  to  their  homes.  The  smooth  seeds 
they  do  not  eat,  but  cast  them  out  of 
their  nests  after  using  the  part  they  like ; 
Fig.  53. -A  view  of  a  ^ftcr  bciug  rcjccted  tlic  seed  may  stand 
seed  of  euphorbia     ^  chaucc  to  arerminate.     The  seeds  can- 

with  a  soft  bunch  at  <^ 

one  end,  a  handle  for     ^ot  bc  Carried  SO  wcll  uulcss  tliis  ridge, 

ants.  . 

caruncle,  be  present.  Other  seeds  of  this 
nature  are  those  of  wild  ginger,  celandine,  cyclamen, 
violet,  periwinkle,  some  euphorbias,  bellwort,  trillium, 
prickly  poppy,  dutchman's  breeches,  squirrel-corn,  several 
species  of  Corydalis,  Seneca  snakeroot,  and  other  species 
of  milkworts. 

In  his  work  on  Vegetable  Mold  and  EarthiDornis,  p.  113, 
Darwin  states  that  earthworms  are  in  the  habit  of  lining 
their  holes,  using  seeds  among  other  things,  and  that  these 
sometimes  grow.  In  this  way  the  worms  aid  in  spreading 
plants. 

43.  Cattle  carry  away  living  plants  and  seeds.  — In  Ari- 
zona, where  cacti  abound,  Professor  Tourney  finds  that 


PLANTS   THAT  ARE   CARRIED  BY  ANIMALS.      71 

many  of  them  are  broken  in  pieces  by  cattle,  which  eat 
a  portion,  while  other  portions  often  adhere  to  the  legs  or 
noses  and  are  carried  from  place  to  place.  These  frag- 
ments are  usually  capable  of  growing. 

The  unicorn  plant,  May^tynia  prohoscidia,  common  in  the 
southwestern  portion  of  the  United  States,  is  sometimes 


Fig.  54.  —  Dry  fruit  of  the  unicorn  plant  adapted  to  catching  on  to  the  feet  of 
large  animals  or  the  wool  of  sheep. 

seen  in  cultivation.  When  ripe,  the  fruit  is  hard,  carrying 
two  stout  beaks  with  recurved  tips.  Exiaeriments  show  it 
to  be  admirably  adapted  to  catch  on  to  the  feet  of  sheep, 
goats,  and  cattle,  or  hold  to  the  fleeces  of  the  two  former. 
44.  Water-fowl  and  muskrats  carry  seeds  in  mud.  — 
Seeds  and  fruits  of  aquatic  and  bog  plants  that  are  float- 
ing, or  in  the  mud  of  shallow  water,  are  often  carried  by 
ducks,  herons,  swallows,  muskrats,  and  other  frequenters 
of  such  places,  on  their  feet,  beaks,  or  feathers,  as  they 


72  SEED  DISPERSAL. 

hastily  leave  one  place  for  another.  In  this  way  seeds  of 
water  plantain,  sedges,  grasses,  rushes,  docks,  arrowhead, 
pondweeds,  duckweed,  cat-tail  flag,  bur  reed,  bladderwort, 
water  crowfoot,  and  many  others  are  transported  from 
one  pond,  lake,  or  stream,  to  another.  In  some  cases 
enough  of  a  living  plant  may  be  detached  and  carried 
away  to  keep  on  growing.  Darwin  found  on  the  feet  of 
some  birds  six  and  three-quarter  ounces  of  mud,  in  which 
were  five  hundred  and  thirty-seven  seeds  that  germinated. 
Mud  may  be  carried  on  the  feet  of  land  animals  as  well 
as  on  aquatic  animals,  not  only  from  ponds  and  bogs,  but 
from  the  fields  where  seeds  may  have  accumulated  in  the 
earth  or  washed  down  the  slopes. 

45.  Why  some  seeds  are  sticky.  —  Some  seeds  and  fruits 
are  sticky  ;  in  some  instances  the  mucilaginous  substance 
is  normally  moist  enough  to  adhere  to  anything  that  touches 
it,  while  in  other  cases  it  requires  to  be  wetted  before  it 
will  adhere.  The  seeds  of  flax,  plantain,  peppergrass, 
basil,  sage,  dracocephalum,  groundsel,  drop-seed  grass,  and 
many  others  less  familiar,  possess  this  peculiarity.  The 
berries  of  some  plants,  when  fully  ripe,  burst  very  easily 
when  touched,  and  some  of  the  seeds  are  then  likely  to 
adhere  to  animals  and  be  carried  away.  Some  berries  of 
several  plants  belonging  to  the  nightshade  family  have 
this  peculiarity,  as  well  as  some  of  the  cucurbits.  When 
the  outer  covering  of  seeds  of  water  lilies,  arums,  and 
others  are  broken,  the  gummy  secretion  is  very  likely  to 
adhere  to  tlie  feathers,  or  fur,  or  feet  of  animals.     A  num- 


PLANTS   THAT  ARE   CARRIED   BY  ANIMALS.      73 

ber  of  fruits,  and  even  the  upper  fruit-bearing  branches, 
have  sticky  glands  with  which  to  catch  on  to  any  passing 
object.  Among  these  are  some  kinds  of  sedges,  chick- 
weeds,  and  catchfiies. 

The   sticky  substance  on  seeds  and   fruits  not    unfre- 
quently  serves  anotlier  good  turn  besides  enabling  them 
to  adhere  to  animals.     The  slime  holds  them  to 
the  spot  where  they  are  to  grow,  or  it  enables 
some  to  float  or  to  sink  in  water,  according  to 
the  amount  of  the  mucilage. 

46.  Three  devices  of  Virginia  knot  weed.  —  A 
perennial  plant,  four  to  Ave  feet  higli,  grows  on 
low  land,  usually  in  the  shade. 
It  is  Polygonum  Virginicum, 
and  so  far  without  a  common 
name,  unless  Virginia  knotweed 
be  satisfactory.  It  is  a  near 
relative  of  knot  grass  and  smart- 
weed  and  Prince's  feather.  The 
small  flowers  are   borne  on  a 

1  1       +■  A  4-11  f'-PP     Fig.  55.  —  Fruit  of  Virginia  knotweed 

long,  elastic,   ana   ratner   stiir     ^^^^^  ^^  gjj,,^,^  ^^  ^.^^^^^  shaken,  or 
stem,  and  each  flower  stalk  has     *«'«*  g«  °^  ^^^™  ^"'i  ''•'^^'^^  ''^  *« 

'  passing  animal. 

a  joint  just   at  the  base.     As 

this  fruit  matures,  the  joint  becomes  very  easy  to  separate. 
It  dries  with  a  tension,  so  that,  if  touched,  the  fruit  goes 
with  a  snap  and  a  bound  for  several  feet.  The  shaking 
produced  by  the  wind  jostling  several  against  each  other 
is  sufficient  to  send  off  a  number  of  ripe  fruits  in  every 


74  SEED  DISPERSAL. 

direction.  Like  many  other  plants  we  have  seen,  this 
has  more  than  one  way  of  scattering  seeds,  and  often 
more  than  two  ways.  Observe  the  slender,  stiff  beak, 
terminating  in  two  recurved  points.  Let  a  person  or 
some  animal  pass  into  a  patch  of  these  plants,  and  at  once 
numerous  fruits  catch  on  wherever  there  is  a  chance,  and 
some  are  shot  upon  or  into  the  fleeces  of  animals,  there  to 
find  free  transportation  for  uncertain  distances.  Should 
there  be  a  freshet,  some  of  these  fruits  will  float ;  or,  in 
case  of  shallow  currents  after  a  rain,  some  of  them  are 
washed  away  from  the  parent  plant.  Any  inquisitive 
person  cannot  fail  to  be  pleased  if  he  experiment  with 
the  plant  when  the  fruit  is  ripe. 

47.  Hooks  rendered  harmless  till  time  of  need.  —  There 
are  a  number  of  rather  weedy-looking  herbs,  common  to 
woods  or  low  land,  known  as  Avens,  Geum.  They  are 
closely  allied  to  cinquefoil,  and  all  belong  to  the  rose  fam- 
ily. The  slender  stiles  above  the  seed-like  ovaries  of  some 
species  of  Avens  are  described  as  not  jointed,  but  straight 
and  feathery,  well  adapted,  as  we  might  suppose,  to  be 
scattered  by  the  aid  of  wind  ;  while  others  are  spoken  of 
as  having,  when  young,  stiles  jointed  and  bent  near  the 
middle.  In  ripening,  the  lower  part  of  the  stile  becomes 
much  longer  and  stouter.  When  a  whole  bunch  of  pistils 
has  drawn  all  the  nourishment  possible,  or  all  that  is  needed, 
from  the  plant  mother,  the  upper  part  of  each  stile  drops 
off,  leaving  a  sharp,  stiff  hook  at  the  end.  At  this  time 
each  pistil  loosens  from  the  torus  and  can  be  easily  removed, 


PLANTS   THAT  ARE   CARRIED  BY  ANIMALS.      75 


especially  if  some  animal  touch  the  hooks.  To  help  in 
holding  fast  to  animals,  there  are  a  number  of  slender 
hairs  farther  down  the  stile,  which  are  liable  to  become 
more  or  less  entangled  in  the  animal's  hair,  fur,  wool,  or 
feathers.  Even  in  the  small  number  of  plants  here  noticed, 
we  have  seen  that  scarcely  any  two  of 
them  agree  in  the  details  of  their  devices 
for  securing  transportation  of  seeds.  I 
know  of  nothing  else  like  the  Geum  we 
are  now  considering.  When  young  and 
green,  the  tip  of  each  hook  is  securely 
protected  by  a  knob  or  bunch,  with  a 
little  arm  extending  above,  which  effect- 
ually prevents  the  hook  from  catching 
on  to  anything;  but,  when  the  fruit  is 
ripe,  the  projecting  knob  with  its  little 
attachment  disappears.  The  fig- 
ures make  further  description 
unnecessary.  To  keep  the  plow 
from  cutting  into  the  ground 
while  g-oing;  to  or  from  the  field, 
the  farmer  often  places  a  wooden 
block,  or  "  shoe,"  over  the  point  and  below  the  plow. 
Sometimes  we  have  known  persons  to  place  knobs  of 
brass  or  wood  on  the  tips  of  the  sharp  horns  of  some  of 
their  most  active  or  vicious  cattle,  to  prevent  them  from 
hooking  their  associates  or  the  persons  having  them  in 
charge.     Nature  furnishes  the  points  of  the  young  fruits 


Fig.  56.  —  The  pistel  of  Avens  in 
three  stages  of  its  growth. 


76  SEED  DISPERSAL. 

of  some  species  of  Avens  with  knobs,  or  shoes,  for  another 
pnrpose,  to  benefit  the  plants  withont  reference  to  the 
likes  or  dislikes  of  animals. 

48.  Diversity  of  devices  in  the  rose  family  for  seed  sow- 
ing. —  All  botanists  now  recognize  plants  as  belonging  to 
separate  families,  the  plants  of  each  family  having  many 
points  of  structure  in  common.  Among  these  families  of 
higher  plants,  over  two  hundred  in  number,  is  one  known 
as  the  rose  family.  Notwithstanding  their  close  relation- 
ship, the  modes  of  seed  dispersion  are  varied.  The  seeds 
of  plums  and  cherries  and  hawthorns  are  surrounded  by  a 
hard  pit,  or  stone,  which  protects  the  seeds,  while  animals 
eat  the  fleshy  portion  of  the  fruit.  Wlien  ripe,  raspberries 
leave  the  dry  receptacle  and  look  like  miniature  thimbles, 
while  the  blackberry  is  fleshy  throughout.  The  dry,  seed- 
like fruits  of  the  strawberry  are  carried  by  birds  that  relish 
the  red,  fleshy,  juicy  apex  of  the  flower  stalk. 

Each  little  fruit  of  some  kinds  of  Avens  has  a  hook  at 
the  apex,  while  in  Agrimony  many  hooks  grow  on  the  out- 
side of  the  calyx  and  aid  in  carrying  the  two  or  three  seeds 
within.  Plants  of  some  other  families  illustrate  the  great 
diversity  of  modes  of  dispersion  as  well  as  the  roses. 

49.  Grouse,  fox,  and  dog  carry  burs.  —  To  the  feathers 
of  a  ruffed  grouse  killed  in  the  molting  stage,  early 
in  September,  were  attached  fifty  or  more  nutlets  of 
EcMnospeymum  Virginicum  Lehm. 

A  student  tells  of  a  tame  fox  kept  near  his  home,  on 
the  tail  of  which  were  large  numbers  of  sand  burs,  and  a 


PLANTS   THAT  ARE   CARRIED  BY  ANIMALS.      77 


smaller  number  on  his  legs  and  feet.  Another  student 
has  seen  dogs  so  annoyed  by  these  burs  on  their  feet  that 
they  gave  up  all  attempts  to  walk. 

Many  wild  animals  unwillingly  carry  about  such  fruits, 
and  after  a  while  most  of  them  remove  what  they  can 
with  claws,  hoof,  or  teeth.     Many  of  these  plants  have  no 


Fig.  59.  —  Fruit  of 


Fig.  58.  —  Nutlet  of  stickseed, 
Echlnospermum. 


Fig.  57. -Whole  ripe  fruit    familiar  comuiou  namcs, 

of  the  coiuiuon  carrot.  ^ 

but  who  has  not  heard  of 
some  of  these  ?  enchanter's  nightshade,  bed- 
straw,  wnld  liquorice,  hound  s  tongue,  beggar-  pitchforks,  ^ide«s, 
ticks,  beggar's  lice,  stick-tights,  pitchforks,  l^,^'^""  ^""^"^ 
tick-trefoil,  bush  clover,  motherwort,  sand 
bur,  burdock,  cocklebur,  sanicle,  Avens,  Agrimony,  carrot, 
horse  nettle,  buffalo  bur,  Russian  thistle.  Besides  these,  a 
very  large  number  of  small  seeds  and  fruits  are  rubbed 
off  and  carried  away  b}^  animals.  Some  of  these  stick  by 
means  of  the  pappus,  as,  for  instance,  the  dandelion,  this- 
tle, prickly  lettuce ;  others  by  means  of  hairs  on  the  seed, 
such  as  those  of  the  willow-herb  and  milkweeds  and 
willows ;   or  by  hairs  on  the  fruit,   as  virgin's   bower, 


78 


SEED  DISPERSAL. 


anemone,    cotton   grass,   and   cat-tail   flag.      These   last 
named  are  apparently  designed  to  be  wafted  by  the  wind. 


Fig.  60. — A  fruit  of  tick-trefoil,  Desmodium,  and  a  few  of  the 
grappling  liooks  enlarged. 

but  they  are  ever  ready  to  improve  any  other  opportunity 
offered,  whether  it  be  by  water  or  by  clinging  to  passing 
animals. 

50.    Seeds  enough  and  to  spare.  —  In   producing    seeds 
nature  is  generous,  often  lavish.     Most  seeds  are  eaten  by 


Fig.  61.  —  a  head  of  the 
fruits  of  burdock. 


Fig.  62.  —  Fruit  of 
cocklebur. 


animals,  or  fall  in  places  where  they  cannot  germinate  and 
produce  plants,  or  fall  in    such   numbers    that  most  of 


PLANTS   THAT  ARE   CARRIED   BY  ANIMALS.      79 

tliem  in  growing  are  crowded  and  starved  to  death.  A 
very  small  proportion  fall  on  good  ground,  and  succeed  in 
becoming  fruiting  plants.  A  large  plant  of  purslane  pro- 
duces one  million  two  hundred  and  fifty  thousand  seeds  ; 
a  patch  of  daisy  fleabane,  three  thousand  seeds  to  each 
square  inch  of  space  covered  by  a  plant.  The  genuine 
student  will  not  be  satisfied  till  he  has  selected  several 
different  kinds  of  plants  and  counted,  or  estimated,  the 
number  of  seeds  produced  by  each,  or  the  number  of  seeds 
furnished  to  the  area  covered  by  one  or  by  several  plants. 


CHAPTER  VIII. 

MAN  DISPERSES  SEEDS  AND  PLANTS. 

In  describing  the  various  means  by  which  plants  are 
dispersed,  people  are  very  likely  not  to  mention  the  aid 
supplied  by  man,  or  to  speak  of  his  efforts  as  artificial  or 
unnatural,  forgetting  for  the  time  that  man  so  far  appears 
to  be  the  crown  of  earthly  existence,  and  that  his  works 
are  a  necessary  part  of  a  complete  world. 

51.  Burs  stick  to  clothing.  —  Late  in  summer  or  in 
autumn,  who  is  there  who  has  not  returned  from  a  walk 
along  the  river  or  from  a  tramp  through  thickets  or  the 
open  woods,  to  find  large  numbers  of  half  a  dozen  kinds 
of  seed-like  fruits  sticking  to  his  clothes  ?  When  ripe, 
these  fruits  usually  separate  from  the  parent  plant  very 
easily,  by  a  joint  or  brittle  place  well  provided  for  in  the 
early  part  of  the  season.  In  pursuing  your  way  you  rub 
off'  a  portion  of  these  fruits,  and  at  the  end  of  the  journey, 
or  before,  you  sit  down  in  some  comfortable  spot  and 
deliberately  pick  off  the  unwelcome  stick-tights.  At  such 
times  you  have  been  the  means  of  transporting  seeds,  and 
you  have  left  them  scattered  about  ready  to  grow.  If 
you  ever  were  so  fortunate  as  to  live  on  a  farm,  you  must 
have  seen  your  father  or  his  hired  help  carefully  look 
about  the  field  or  the  wood  lot  and  remove  all  the  bur- 


3fAN  niSPEESES   SEEDS  AND  PLANTS. 


81 


Fig.  63.  —  Seed 
of  cockle 

(enlarged). 


bearing  plants  that  could  be  found  before  turning  in  his 
flock  of  sheep  or  the  colts  and  cattle;  for  if  this  were  not 
done,  he  knows  that  hair  and  mane  will  surely  be  disfig- 
ured, and  that  the  wool  will  be  rendered  un- 
salable. In  removing  the  weeds  he  defeated 
the  plans  of  Nature  in  her  devices  for  sowing 
seeds. 

Tlie  agency  of  man  in  the  distribution  of 
plants  exceeds  in  importance  that  of  all  other 
means  combined.  He  buys  and  sells  seeds  and 
plants,  and  sends  them  to  all  parts  of  the 
habitable  globe.  He  exterminates  many  plants  in  large 
areas,  and  substitutes  m  large  measure  those  of  his  choice. 
Mixed  with  seeds  of  grasses,  clovers,  or  grains, 
he  introduces  many  weeds  and  sows  them  to 
grow  with  his  crops. 

L.  H.  Dewey,  in  the  Yearbook  of  the  De- 
partment of  Agriculture  for  the  year  1896, 
p.  276,  says :  "  Cockle  seeds  are  normally 
somewhat  smaller  than  wheat  grains.  In 
some  parts  of  the  northwest,  where  wheat  for 
sowing  has  been  cleaned  year  after  year  by 
„     ^.     ^   .     steam  threshers,  all  the  cockle  seeds  except 

Fig.  64.  —  Gram  '  i 

of  wiieat  (en-   tlic  largcst  oncs  have  been  removed,  and  these 

larged),  scarce-  ,  -i  i  i     t        ,        • 

ly  larger  than  a   havc   Dceu   sowu  uutil   a  large-seeded  stram 

seed  of  cockle.      i  i  i  t        i   •    t       •  i  •  rf        1 1     i 

has  been  bred  which  is  very  dimcult  to  sepa- 
rate from  the  wheat."  For  illustration,  some  years  ago  I 
purchased  of  a  dealer  in  Michigan  a  small  quantity  of 


82 


SEED  DISPERSAL. 


what  was  being  sold  on  the  market  as  seed  of  red  clover ; 
this  specimen  contained  40  per  cent  of  seeds  of  rib-grass 
or  narrow-leaved  plantain. 

Man   introduces  some  seeds  of  weeds  with  uno-round 
feed  stuff.     He  introduces  some  with  barnyard  manure 

drawn  from  town.  He  gets  some 
in  the  packing  of  nursery  stock, 
crockery,  baled  hay  and  straw. 
For  example,  in  1895,  baled  hay 
from  Kansas  or  that  vicinity  ex- 
amined at  the  Missouri  Agricultural 
College  was  found  to  contain  fifteen 
species  of  weeds.  Others  from  the 
west  were  examined  in  Michigan 
and  found  to  contain  much  foul 
stuff.  Some  are  carried  from  farm 
to  farm  by  wagons,  sleighs,  or 
threshing  machines ;  or  they  are  spread  by  plows,  culti- 
vators, and  harrows.  A  few  are  introduced  to  grow  for 
ornament  or  food,  and  afterwards  spread  as  weeds.  A 
number  have  been  shipped  to  distant  lands  in  the  earth 
of  ballast,  which  is  often  unloaded  and  reloaded  at  wharves 
where  freight  is  changed.  They  are  carried  along  the 
highway,  strung  along  the  towpath  of  canals,  or  are 
carried  in  the  trucks  or  in  the  cars  of  railroads.  They 
are  imported  and  exported  around  the  world  in  fleeces  of 
wool.  They  float  down  irrigating  ditches  from  farm  to 
farm,  and  with  the  water  are  well  distributed. 


Fig.  65.  —  Two  seeds  of  narrow- 
leaved  plantain  sucli  as  are  be- 
coming common  in  clover  seed. 
The  lower  one  and  the  one  at 
the  left  are  seeds  of  red  clover. 


MAN  DISPERSES  SEEDS  AND   PLANTS.  83 

52.  Man  takes  plants  westward,  though  a  few  migrate 
eastward.  —  So  far  as  man's  agency  is  concerned,  the 
direction  for  plant  migration  is  generally  westward,  in 
the  course  taken  by  himself.  In  case  of  two  hundred 
kinds  of  weeds  named  by  the  United  States  Department 
of  Agriculture,  one  hundred  and  eight  species  are  of 
foreign  origin.  Three  notable  samples  of  weeds  in  the 
United  States  have  gone  from  the  west  to  the  east,  carried 
in  seeds  of  grasses  or  clovers.  These  are  Rudheckia  hirta, 
Artemisia  biennis,  Plantago  aristata.  To  these  Mr.  Dewey 
adds  buffalo  bur,  Solanum  rostratum,  squirreltail,  Hordemn 
juhatum,  false  ragweed  or  marsh  elder,  Iva  xanthi/olia, 
Franseria  liookeriana,  alfalfa  dodder,  Cuscuta  epithymum. 

Above  I  have  barely  mentioned  a  few  of  the  methods 
by  which  man  is  an  unwilling  agent  in  distributing  plants. 
Larg;e  volumes  could  be  filled  with  statements  of  man's 
more  or  less  carefully  planned  attempts  to  transport  seeds 
and  living  plants  from  one  part  of  the  world  to  another. 


CHAPTER  IX. 
SOME  REASONS  FOR  PLANT  MIGRATION. 

53.  Plants  are  not  charitable  beings.  —  Man  uses  to  his 
advantage  a  large  number  of  plants,  but  there  appears  to 
be  no  evidence  that  the  schemes  for  their  dispersion  were 
designed  for  anything  except  to  benefit  the  plants  them- 
selves. The  elegant  foliage  and  beautiful  flowers,  the 
great  diversity  of  attractive  seeds  and  fruits,  all  point  to 
plants  as  strictly  selfish  beings,  if  I  may  so  use  the  term ; 
and  not  to  plants  as  works  of  charity,  to  be  devoured  by 
animals  without  any  compensation.  By  fertilizing  flowers, 
by  distributing  plants,  and  by  other  helpful  acts,  animals 
pay  for  at  least  a  portion  of  the  damage  they  do. 

By  an  almost  infinite  number  of  devices,  we  have  seen 
that  seeds  and  fruits  flee  from  the  parental  spot  on  the' 
wings  of  the  wind,  float  on  currents  of  ocean,  lake,  and 
river.  They  are  shot  by  bursting  pods  and  capsules  in 
every  direction.  With  hooks,  barbs,  and  glands  they  cling 
to  the  covering  of  animals.  Allured  by  brilliant  colors, 
birds  and  other  animals  seek  and  devour  the  fruits  of 
many  plants,  the  seeds  of  which  are  preserved  from  harm 
by  a  solid  armor  ;  these  seeds  are  then  sown  broadcast 
over  the  land,  ready  to  start  new  colonies.  Nuts  are  often 
carried  by  squirrels  for  long  distances,  and  there  securely 


SOME  REASONS  FOR   PLANT  MIGRATION.         85 

buried,  a  few  in  a  place.  By  a  slow  process,  which,  how- 
ever, covers  a  considerable  space,  in  a  few  years  many 
plants  send  forth  roots,  rootstalks,  stolons,  and  runners, 
and  thus  increase  their  possessions  or  find  new  homes. 

54.  Plants  migrate  to  improve  their  condition.  —  The 
various  devices  by  which  plants  are  shifted  from  place  to 
place  are  not  merely  to  extend  and  multipl}^  the  species, 
and  reach  a  fertile  soil,  but  to  enable  them  to  flee  from 
the  great  number  of  their  own  kind,  and  from  their  ene- 
mies among  animals  and  parasitic  plants.  The  adven- 
turers among  plants  often  meet  with  the  best  success,  not 
because  the  seeds  are  larger,  or  stronger,  or  better,  but 
because  they  find,  for  a  time,  more  congenial  surround- 
ings. We  must  not  overlook  the  fact,  so  well  established, 
that  one  of  the  greatest  points  to  be  gained  by  plant  migra- 
tion is  to  enable  different  stocks  of  a  species  to  be  cross  fer- 
tilized, and  thereby  improved  in  vigor  and  productiveness. 

55.  Fruit  grown  in  a  new  country  is  often  fair.  —  Every 
horticulturist  knows  that  apples  grown  in  a  new  country, 
that  is  suited  to  them,  are  healthy  and  fair;  but,  sooner 
or  later,  the  scab,  and  codling  moth,  and  bitter  rot,  and 
bark  louse  arrive,  each  to  begin  its  particular  mode  of 
attack.  Peach  trees  in  new  places,  remote  from  others, 
are  often  easily  grown  and  free  from  dangers;  but  soon 
will  arrive  the  j^ellows,  borers,  leaf  curl,  rot,  and  other 
enemies.  For  a  few  years  plums  may  be  grown,  in  cer- 
tain new  localities,  without  danger  from  curculio,  or  rot, 
or  shot-hole  fungus.      It  has  long  been  known  that  the 


86  SEED   DISPERSAL. 

nicest  way  to  grow  a  few  cabbages,  radishes,  squashes, 
cucumbers,  or  potatoes  is  to  plant  a  few  here  and  there  in 
good  soil,  at  considerable  distances  from  where  any  have 
heretofore  been  grown.  For  a  time  enemies  are  not  likely 
to  find  them.  I  have  often  noticed  that,  while  pear-blight 
decimated  or  swept  large  portions  of  a  pear  orchard,  a  few 
isolated  trees,  scattered  about  the  neighborhood,  usually 
remain  healthy.  The  virgin  soil  of  the  Dakotas  produced, 
at  a  trifling  cost,  healthy,  clean  wheat,  but  it  was  not  long 
before  the  Russian  thistle,  false  flax,  and  other  pests  fol- 
lowed, to  contest  their  rights  to  the  soil. 

As  animals  starve  out,  in  certain  seasons  when  food  is 
scarce,  or  more  likely  migrate  to  regions  which  can  afford 
food,  so  plants  desert  worn-out  land  and  seek  fresh  fields. 
As  animals  retreat  to  secluded  and  isolated  spots  to  escape 
their  enemies,  so,  likewise,  many  plants  accomplish  the 
same  thing  by  sending  out  scouts  in  all  directions  to  find 
the  best  places  ;  these  scouts,  it  is  needless  to  say,  are 
seeds,  and  when  they  have  found  a  good  place,  they 
occupy  it,  without  waiting  for  further  instructions. 

56.  Much  remains  to  be  discovered.  —  "•  In  this,  as  in 
other  branches  of  science,  we  have  made  a  beginning. 
We  have  learned  just  enough  to  perceive  how  little  we 
know.  Our  great  masters  in  natural  history  have  immor- 
talized themselves  by  their  discoveries,  but  they  have  not 
exhausted  the  field ;  and  if  seeds  and  fruits  cannot  vie 
with  flowers  in  the  brilliance  and  color  with  which  they 
decorate  our  gardens  and  our  fields,  still  they  surely  rival 


SOME  REASONS  FOR   PLANT  MIGRATION         87 

tliein  —  it  would  be  impossible  to  excel  them  —  in  the 
almost  infinite  variety  of  the  problems  they  present  to 
us.  the  ingenuity,  the  interest,  and  the  charm  of  the  l^eau- 
tiful  contrivances  which  they  offer  for  our  study  and  our 
admiration."  ^ 

Frequent  rotations  seem  to  be  the  rule  for  many  plants, 
when  left  to  themselves  in  a  state  of  nature.  Confining  to 
a  permanent  spot  invites  parasites  and  other  enemies,  and 
a  depleted  soil,  while  health  and  vigor  are  secured  by 
frequent  migrations.  The  more  we  study  in  detail  the 
methods  of  plant  dispersion,  the  more  we  shall  come  to 
agree  with  a  statement  made  by  Darwin  concerning  the 
devices  for  securing  cross-fertilization  of  flowers,  that  they 
"transcend,  in  an  incomparable  degree,  the  contrivances 
and  adaptations  which  the  most  fertile  imagination  of  the 
most  imaginative  man  could  suggest  with  unlimited  time 
at  his  disposal."  ^ 

Let  no  reader  think  that  the  topics  here  taken  up  are 
treated  exhaustively,  for  if  he  will  go  over  any  part  of 
this  work  and  verify  any  observation  or  experiment,  he  will 
be  sure  to  find  something  new,  and  very  likely  something 
different  from  what  is  here  stated. 

^  Floicers,  Fruits,  and  Leaves,  by  Sir  John  Lubbock,  p.  96. 
^Fertilization  of  Orchids,  p.  351. 


BIBLIOGRAPHY. 


Means  of  Plant  Dispersion.  Ry  E.  J.  Hill.  Am.  Nat.  Vol.  xvii,  pp.  811, 
1028.     1888. 

Wliy  Certain  Kinds  of  Timber  Prevail  in  Certain  Localities.  By  John  T. 
Campbell.     Am.  Nat.     Vol.  xix,  p.  337.     1885. 

■Report  of  the  U.  S.  Commissioner  of  Agriculture  for  1888.  Article  on  the 
"  Food  of  Crows."     By  W.  B.  Barrows,     p.  498. 

Keport  of  the  U.  S.  Secretary  of  Agriculture  for  1890.  Article  on  "Seed 
Planting  by  Birds."     By  AV.  B.  Barrows,     p.  280. 

Report  of  the  U.  S.  Secretary  of  Agriculture  for  1893.  Article  on  "  Food 
Habits  of  the  Kingbird,  or  Bee  Martin."     By  W.  B.  Barrows,     p.  233. 

Bulletin  Xo.  6,  U.  S.  Department  of  Agriculture.  Division  of  Ornithol- 
ogy and  ^lammology.  "  The  Common  Crow  of  the  United  States." 
By  W.  B.  Barrows  and  E.  A.  Schwarz.     1895. 

Bulletin  Xo.  7,  U.  S.  Department  of  Agriculture.  Division  of  Ornithology 
and  Mammology.     "  Food  of  Woodpeckers."     By  F.  E.  L.  Beal. 

Causes  of  Forest  Rotation.  By  John  T.  Campbell.  Am.  JVat.  Vol.  xx, 
p.  521.     1886. 

Seeds  of  the  Violet  and  Other  Plants  as  Projectiles.  By  Moses  X.  El- 
rod,  M.D.     Am.  Nat.     Vol.  xiii,  p.  93.     1879. 

The  Natural  History  of  Plants.  By  Kerner  and  Oliver.  Henry  Holt 
&  Co.,  Xew  York.     1895. 


90  BIBLIOGRAPHY. 

Flowers,  Friiits,  and  Leaves.     By  Sir  John  Lubbock.     Macmillan  &  Co., 
New  York. 

Origin  of  Cultivated  Plants.     By  Alphonse  De  Candolle.     D.  Appleton 
&  Co.,  New  York. 

Distribution  of  Weed  Seeds  by  Winter  Winds.     By  H.  L.  Bolley.     Bul- 
letin No.  17.     Fargo,  North  Dakota. 

Weeds  of  California.     By  E.  W.  Hilgard.     Report  of  the  Experiment 
Station,  pp.  238-266.     1890. 

Migration  of  Weeds.     By  L.  H.  Dewey.     Yearbook  of  the  U.  S.  Depart- 
ment of  Agriculture,  pp.  263-286.     1896.     Washing-ton,  D.  C. 

Squirrels  Carrying  Nuts.     Nature.     Vol.  xv,  p.  117.     Macmillan  &  Co., 
New  York. 

Natural  History  of  Plants.     By  Kerner  and  Oliver.     Distribution  of 
Species.     Vol.  ii,  pp.  790-885.     Henry  Holt  &  Co.,  New  York.     1895. 


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